CONCHOLGY

Conchology. CONCHOLGY is that branch of Natural History, which makes us acquainted with the form and structure of shells, enables us to classify them according to their external characters, and prepares us for the examination of the Molluscous animals to which they afford protection. It has frequently been confounded with Crustaceology, especially by the older writers on Natural History, who were in a great measure ignorant of the organization of the less perfect animals, and incapable of fixing the limits of kindred tribes. But between testaceous and crustaceous animals the line of separation is well defined, whether we attend to the composition of the covering, or to the structure of the contained animal. The shells of the former are principally composed of carbonate of lime, united with a small portion of animal matter in the form of gelatine or coagulated albumen; the crusts of the latter, along with animal matter and carbonate of lime, contain also a considerable quantity of phosphat of lime. The difference, however, between the two tribes, is much more strongly marked, when we examine the animals to which these coverings belong. The testaceous animals are remarkable for the softness of their bodies, the continuity of their parts, the simplicity of their mouth, and the permanency of their attachment to their calcareous dwellings. The crustaceous animals, on the other hand, have a fibrous texture, articulated members, complicated organs of mastication, and, at stated periods, renew their coverings. Testaceous bodies have likewise been confounded with the Echinodermata (a class which includes the sea urchins and the star-fish) not only by Aristotle, but by many modern naturalists. But the crusts with which these animals are covered, contain the same ingredients as are found in the coverings of the crustacea; and the animals themselves are furnished with prehensile tentacula. Hence they are essentially different from the testacea, and appear to be more nearly related to the Zoophytes, with which Rondeletius, and, after him, Cuvier, united them.

In taking a view of this extensive subject, we propose to confine our remarks to the consideration of testaceous bodies as objects of utility—of amusement—of scientific arrangement,—and lastly, as objects of interest to the geologist. In the body of the work the reader will find many valuable synoptical tables of the systems of different authors, and an extensive list of species, with their characters, arranged according to the Linnæan method.

Testaceous Bodies considered as Objects of Utility.

Although testaceous bodies furnish many articles of value to man, scarcely any Conchologist has taken the trouble to enumerate the different purposes to which they have been applied, or to point out in what manner their usefulness might be increased. To the savage, shells furnish some of his most important instruments. They often answer all the purposes of a knife, and are extensively employed as a

substitute for iron: with pieces of the more solid bivalves he points his arrows, and forms his fish-hooks. Even when farther advanced in civilization, the calcareous univalves sometimes constitute the rustic lamp, while the larger scallops are employed by the dairy-maid to skim her milk and to slice her butter. From the mother-of-pearl shell many useful and ornamental articles are fabricated; and calcined shells were formerly esteemed by Physicians as absorbents; and are still regarded by the farmer as furnishing a valuable manure.

Shells thus appear to be of some importance in the arts of life; but the animals contained in these shells are of far greater value. As articles of food, shell-fish are extensively employed by the poor, and even hold a conspicuous place at the tables of the rich. In many places, they in a great measure support the children of our maritime population, and, in the Western and Northern Islands of Scotland, have, in years of scarcity, prevented the death of thousands.

The kinds chiefly used in this country, as articles of subsistence, are bivalves, belonging to different genera. Among these the Oyster (Ostrea edulis) holds the most distinguished place. This shell-fish is very widely distributed in nature, being found in the seas of Europe, Asia, and Africa. But, since the days of the luxurious Romans, the oysters of Britain have been held in the highest estimation. They are found on various parts of our coasts, from the southern shores of England, to the sheltered bays among the Zetland Islands. They prefer a rough or rocky bottom, in from five to twenty fathoms water. They are fished up with a dredge and an open boat; sometimes, when in shallow water, with a rake or tongs. They are either conveyed directly to the market, or are placed in artificial ponds of sea water, where they increase in size, and acquire a fine green colour. In England this process of fattening, as it is termed, is chiefly conducted at Colchester, but the oysters are obtained from the little creeks between Southampton and Chichester. This fishery on the coast of England is supposed to give employment to ten thousand people, so that, independent of the addition which it makes to the articles of subsistence, it must be regarded as a valuable nursery for seamen. As an article of food, oysters are light and easy of digestion, and may be eaten in great numbers without inconvenience. They are used either raw or when pickled. In the last form, they are sent to different parts of the country, and even constitute an article of export. In Scotland, the principal oyster fishings are in the Firth of Forth; but we trust the period is not far distant, when the proprietors on the western coast of Scotland and the Hebrides will propagate this shell-fish more extensively on their shores and sheltered bays. Places fitted for their growth are every where to be met with; they require no superintending care; they would soon furnish an

Conchology. esteemed dish to their tables, and form a valuable addition to their trade.

Mussel. The next shell-fish, in point of importance as an article of food, is the Mussel (Mytilus edulis). This animal is equally widely distributed as the oyster, and is found upon our coast in the greatest abundance. It is gregarious, being found in extensive beds, which are always uncovered at low water. It is found likewise in the crevices of the rocks. In this fishery women and children are chiefly employed, and they detach the mussels with an iron hook from the beds or rocks to which they adhere by means of fine cartilaginous threads. In this country they are conveyed directly to the market; but in some places of France they are kept for a time in salt ponds, to fatten like the oyster, into which, however, they admit small quantities of fresh water. The flesh of the mussel is of a yellowish colour, and considered very rich, especially in autumn, when it is in season. It is eaten in this country either boiled or pickled, seldom in soup. To the generality of stomachs it is difficult to digest, and to many constitutions it is deleterious. It is, however, in the spring, during the spawning season, that the greatest danger is to be apprehended. This noxious quality was long considered as occasioned by the pea crab, which is often found within the shell of mussels. It is now with more propriety attributed to the food of the mussel, which, at certain seasons, consists chiefly of the noxious fry of the star-fish; and likewise to a disease to which the animal is subject in spring, under the influence of which it melts away, and falls from the rocks. Besides being useful to man as an article of subsistence, the mussel supplies the fisherman with one of his most convenient and successful baits. It is keenly taken both by cod and haddock. To the cod-fish, however, the animal of the horse-mussel (Modiola vulgaris) is more acceptable.

Cockle. The Common Cockle (Cardium edule) would deserve a place in preference even to the mussel, were it not exclusively confined to our sandy coasts and bays. It is found lodged in the sand, a few inches below the surface, its place being marked by a small depressed spot. Women and children easily dig up this shell-fish with a small spade. Cockles are sold by measure, and eaten either raw, or boiled, or pickled. They are deservedly esteemed a delicious and wholesome food in this country, although in France they are little regarded. They are in season during March, April, and May, after which they become milky and insipid. They are not generally used as a bait.

Razor-fish. Two kinds of Razor-fish (Solen siligua and ensis) are in many places of this country used as food. In Scotland they are indiscriminately termed Spout-fish. They are found upon most of our sandy shores, buried about a foot or two below the surface, and near to the low water mark. Their place is known by a small hole in the sand. As it is rather a laborious operation to dig them out, Bosc informs us, that the fishermen of France throw a small pinch of salt into their holes, which always remain open by the action of the respiratory organs; that they speedily rise to the surface, and are thrown out by an iron instru-

ment made for the purpose. The fishermen believe Conchology. that it is the salt which they wish to avoid; but it is conjectured, with greater probability, that the presence of the salter water, which is thus formed by the solution of the salt, makes the animal suppose that its hole is again covered with the tide. This shell-fish was esteemed by the ancients as a great delicacy. When boiled or fried, it is certainly a very palatable morsel. When kept for a few days, it forms an excellent bait for haddock or cod, and may even be employed for that purpose in a fresh state.

Several species of Gapers (Mya) are used as food Mya. both in Britain and on the Continent, as the Mya arenaria, known to the fishermen about Southampton by the whimsical name Old Maids. These shells reside in the mud or shingle on the shore, and a few inches below the surface. In some parts of England and Ireland, they are much used, but, though common in Scotland, they are never sought after. Another species, the Mya truncata, is also very common on the coast. It prefers a hard gravelly bottom, in which it lodges near low water-mark. The inhabitants of the northern islands call it Smuoslin, and employ it when boiled as a supper dish. It is not so delicate as some of the shell-fish which we have noticed, but it is by no means unpalatable. The Mya declivis of Pennant is, according to that author, very plentiful in the Hebrides, and eaten by the gentry of that country. We suspect that he should have referred to the Mya truncata. These shells furnish very good baits to the fisherman.

There are several bivalve shells, besides those which Scallops. we have mentioned, employed on our coasts as articles of subsistence. The Scallop (Pecten) was held in high estimation by the ancients, and still is sought after in Catholic countries. The Pecten maximus is frequently used in England. It is found gregarious in moderately deep water, and is taken up by the dredge. It is pickled and barrelled for sale, and esteemed a great delicacy. The fishermen suppose that they are taken in the greatest quantity after a fall of snow. Another species, the Pecten opercularis, is employed for culinary purposes in Cornwall, where it is known by the name of Frills or Queens. In the Firth of Forth this species is frequently dredged up along with oysters, but it is thrown, by the Newhaven fishermen, to the dunghill, along with sea urchins and star-fish. To this list we might add the Mactra solida, which is used as food by the common people about Dartmouth; and the Venus pullastra, called by the inhabitants of Devonshire Pullet, and eaten by them, and known to the inhabitants of the Northern Islands by the name of Cullyock, and there used as a bait. According to Bruguiere, the Anomia ephippium is used as food at Languedoc, and is there considered as preferable to the oyster.—But it is now time that we turn our attention to the univalve shells, in order to ascertain their value in an economical point of view.

The common Periwinkle (Turbo littoreus) is, in Univalves. this country, more extensively used as food than any Periwinkle. of the other testaceous univalves. This shell is easily gathered, as it is found on all our rocks which are left uncovered by the ebbing of the tide. Children

Conchology. are principally employed in this fishery, and the shells are sold by measure. They are in general used after being plainly boiled, and are consumed in great quantities by the poor inhabitants on the coast. The Nerita littoralis is also frequently gathered along with the periwinkle, as it frequents the same situations. It is, however, much smaller, and its flesh is not reckoned equally good.

Limpet. The Limpet (Patella vulgata) is equally abundant as the periwinkle, and frequents the same situations on the rocks. Although used by the ancients as an article of food, it is seldom brought to market in this country. Among the villages along the coast of Scotland this shell-fish is frequently used, and its juice, obtained by boiling, mixed with oatmeal, is held in high estimation. It is considered in season about the end of May. The chief excellence of the limpet, however, is as a bait. It is very easily obtained from the rocks, from which the fishermen detach it with a knife, and it is eagerly seized by all the littoral fish which are sought after. To the haddock it is very acceptable.

Snails. Several species of Snails (Helix) are employed for culinary purposes. The largest of these, the Helix pomatia, was a favourite dish among the Romans, who fattened them with bran sodden with wine. They are still used in many parts of Europe during Lent, after having been fed with different kinds of herbs. This species was originally imported into Britain from Italy, and turned out in Surrey, where it has readily multiplied. The Helix hortensis has also been employed as food. But, we believe that these two species are chiefly used medicinally, being administered in consumptive cases. The small species of the genus are the favourite food of the birds of the thrush kind, either in a wild or confined state.

Welks. The other univalves which we shall notice are of inferior importance as articles of subsistence. The Murex despectus, the largest of the British turbinated shells, is frequently dredged up with oysters, and, according to Pennant, "is eaten by the poor, but oftener used for baits for cod and ray." It is probably the same species which is noticed by the Reverend William Fraser, in his view of the Parish of Gigha and Cara in Argyleshire, Vol. VIII. p. 48. of the Statistical Account of Scotland. He says it is a large white welk called buckie or dog-welk, and used as a bait for cod. The method of obtaining these shells for bait being ingenious, and making us acquainted at the same time with several new habits of the animal, we shall here insert it. "At the beginning of the fishing (says Mr Fraser) a dog is killed and singed, and the flesh, after rotting a little, is cut into small pieces, and put into creels or baskets made of hazel-wands for the purpose. These creels are sunk by means of stones thrown into them. The flesh of the dog, in its putrid state, is said to attract the welk, which crawls up round the sides of the basket, and getting in at the top, cannot get out again, owing to the shape of it, which is something like that of the wire mouse-trap. After the first day's fishing, the heads and entrails of the cod, with skate and dog-fish, are put into the creels, which are visited every day, the welks taken out, and fresh bait of the same kind put in, there be-

ing no more occasion for dogs' flesh." The Bucci-Conchology, num undatum and the Purpura lapillus are also employed as bait, and in years of scarcity as food.

This list of culinary shell-fish is far from complete, even in so far as it is a British list. The uses of these molluscous animals have seldom been taken notice of by Conchologists since the days of Schonvelde, more attention having been directed to the formation of new systems of arrangement, and to the discovery of new species, than to the habits and uses of those already known.

Independently of the food which we thus obtain Pearls from testaceous animals, they furnish us with the pearl, one of the most beautiful ornaments of dress. This substance, equally prized by the savage and the citizen, is composed, like shells, of carbonate of lime, united with a small portion of animal matter. Pearls appear to be exclusively the production of the bivalve testacea. Among these, all the shells having a mother-of-pearl inside, produce them occasionally. But there are a few species which yield them in greater plenty, and of a finer colour. The most remarkable of these is the Avicula margaritifera. This shell, which was placed by Linnaeus among the mussels, is very widely distributed in the Indian Seas; and it is from it and another species of the same genus, termed Avicula hirundo, found in the European Seas, that the pearls of commerce are procured. The Pinna, so famous for furnishing a byssus or kind of thread, with which garments can be manufactured, likewise produces pearls of considerable size. They have seldom the silvery whiteness of the pearls from the Avicula, being usually tinged with brown. But the shell which in Britain produces the finest pearls, is the Unio margaritifera, which was placed by Linnaeus in the genus Mya. It is found in all our alpine rivers. The Conway and the Irt in England, the rivers of Tyrone and Donegal in Ireland, and the Tay and the Ythan in Scotland, have long been famous for the production of pearls. These concretions are found between the membranes of the cloak of the animal, as in the Avicula, or adhering to the inside of the shell, as in the Unio. In the former case, they seem to be a morbid secretion of testaceous matter; in the latter, the matter seems to be accumulated against the internal opening of some hole with which the shell has been pierced by some of its foes. Linnaeus, from the consideration of this circumstance, endeavoured, by piercing the shell, to excite the animal to secrete pearl; but his attempts, though they procured him a place among the Swedish nobility and a pecuniary reward, were finally abandoned; the process being found too tedious and uncertain to be of any public utility. The largest pearl of which we have any notice, is one which came from Panama, and was presented to Philip II. King of Spain, in 1579. It was of the size of a pigeon's egg. Sir Robert Sibbald mentions his having seen pearls from the rivers of Scotland as large as a bean.

Besides yielding us a variety of wholesome food, Dyes and valuable ornaments, testaceous animals supply us with a beautiful dye. The Purpura of the ancients, according to the opinion of Rondeletius, confirmed by the observations of Cuvier, was chiefly extracted

Conchology. from the shell termed Murex brandaris. Since the introduction of the cochineal insect, the use of this dye has been superseded, so that we are now in a great measure ignorant of the process which the ancients employed to extract it. In Britain there are several kinds of shell-fish, which furnish a dye of this sort, but these are seldom sought after. Cole, in 1685, published a method of obtaining it from the Purpura lapillus, to which Montagu, in the Supplement to Testacea Britannica, has added several important directions. When the shell is broken in a vice, there is seen on the back of the animal, under the skin, a slender longitudinal whitish vein, containing a yellowish liquor. When this juice is applied to linen, by means of a small brush, and exposed to the sun, it becomes green, blue, and purple, and at last settles in a fine unchangeable crimson. Neither acids nor alkalies affect its colour, and it may be conveniently employed in marking linen, where an indelible ink is desirable. The Scalaria clathrus (Turbo clathrus of Linnaeus) also furnishes a purple liquor of considerable beauty, but it is destructible by acids, and gradually vanishes by the action of light. The Planorbis cornus likewise yields a scarlet dye, but of still less permanency than the scalaria, as all attempts to fix it have hitherto proved ineffectual.

We cannot conclude this chapter without remarking, that the study of testaceous bodies rises in importance as we perceive its utility. When we are told, that searching for shell-fish, and conveying them to the market, give employment to a British population of upwards of 10,000; that these animals furnish nourishing food to innumerable families, and in years of scarcity prevent the horrors of famine; we will be disposed to regard with a favourable eye the labours of that Conchologist, who examines the structure and economy of those animals, that, from a knowledge of their nature, he may render them still more subservient to our purposes.

Testaceous Bodies, considered as Objects of Amusement.

Shells as Objects of Amusement.

In the preceding division of our subject, we have considered testaceous bodies as applicable to various useful purposes, and expressed our regret, at the same time, that no one qualified for the task had ever bestowed on economical Conchology an attentive examination. We cannot therefore consider the present condition of the science as the result of the labours of its practical admirers. The lovers of this study, as an agreeable amusement, have at all times been numerous, from the days of Lælius and Scipio to the present time; and it is to their exertions, as collectors, that the science is principally indebted for its present state of improvement. The colours of shells are often so intensely vivid, so finely disposed, and so fancifully variegated, that, as objects of beauty, they rival many of the esteemed productions of the vegetable kingdom. In their forms they likewise exhibit an infinite variety. While some consist merely of a hollow cup or a simple tube, others exhibit the most graceful convolutions, and appear in the form of cones, and spires, and turbans; and in another division, shaped like a box, all the varieties of hinge are exhibited, from that of simple

Conchology. connection by a ligament to the most complicated articulation. The forms of shells are indeed so various, and many of them so elegant, that a celebrated French Conchologist warmly recommends them to the attentive study of the Architect. "Or," says Lamark, "comme l'extrême diversité des parties protubérantes de la surface de ces coquilles, ainsi que la régularité et l'élegance de leur distribution, ne laisse presque aucune forme possible dont la nature n'offre ici des exemples; on peut dire que l'architecture trouveroit dans les espèces de ce genre (Cerithium) de même que dans celles des pleurotomes et des fuseaux, un choix de modèles pour l'ornement des colonnes, et que ces modèles seroient très dignes d'être employés." (Annales du Mus. Vol. III. p. 269.) In this country, however, no such recommendation is necessary, as many of our beautiful ornaments of stucco, particularly for chimney-pieces, are copied from the univalve testacea, and are greatly admired.

But shells, even with all their beauty and elegance, would never have acquired so much importance in the eyes of amateurs, had their forms been as difficult to preserve as the external coverings of the higher classes of animals. It is both a tedious and a difficult operation to preserve a quadruped, a bird, or a fish, as a specimen for the cabinet, and even when the task is completed, it is but of temporary duration. A slow but certain process of dissolution is going on, which, though invisible for a time to the owner, gradually destroys the finest collection of these objects. The very changes of the atmosphere, combined with the attacks of insects, accelerate the destructive process. But with shells the case is very different. Composed of particles already in natural combination, they do not contain within themselves the seeds of dissolution, so that for ages they remain the same. Besides, all that is in general necessary to prepare a shell for the cabinet, is merely to remove the animal. When the shell is covered with foreign matter, we must wash it away with a brush in soap and water; and it is frequently necessary to steep the shell for some time in fresh water, to extract all the salt water which may adhere to it. After being properly dried it is fit for the shelf of the cabinet, and stands in no need of anxious superintendence.

Amateurs are seldom contented with the simplicity of nature. Vitiated in their taste by a fashion of shells, which abides by no rules, they attempt to improve even her most elegant productions, and delight to exhibit in their cabinets some of the efforts of their art. As such are in search of innocent amusement, we mean not to dispute about the propriety of their conduct, but rather shortly to mention, for their edification, the method generally in use to improve the beauty of testaceous objects. Many shells, it is true, naturally possess so fine a polish, that no preparation is considered necessary before placing them in the cabinet. Such are the Cypreas, Olivæ, and the greater number of what are termed porcellaneous shells. In general, however, it happens that, when shells become dry, they lose much of their natural lustre. This may be very easily restored, by washing them with a little water, in which a small portion of gum arabic has

Conchology. been dissolved, or with the white of an egg. This is the simplest of those processes which are employed, and is used not only by the mere collector, but by the scientific Conchologist. There are many shells of a very plain appearance, on the outside, by reason of a dull epidermis or skin with which they are covered. This is removed by soaking the shell in warm water, and then rubbing it off with a brush. When the epidermis is thick, it is necessary to mix with the water a small portion of nitric acid, which, by dissolving a part of the shell, destroys the cohesion of the epidermis. This last agent must be employed with great caution, as it removes the lustre from all the parts exposed to its influence. The new surface must be polished with leather, assisted by tripoli. But, in many cases, even these methods are ineffectual, and the file and the pumice-stone must be resorted to, in order to rub off the coarse external layers, that the concealed beauties may be disclosed. Much address and experience are necessary in the successful employment of this last process. But it must be confessed that the reward is often great. When thus prepared, even the common mussel is most beautiful.

The arrangement of shells in a cabinet must depend, in a great degree, on the taste and fortune of the collector. If ornament is the object in view, it will be indispensably necessary to have the shells placed in glass cases, where they may be distinctly seen. But where a collection of shells is formed for amusement, they may be kept in drawers, each species placed in a paper case, or in a cup of wood, glass, or porcelain, with a label attached, intimating its name, and the place from whence it was obtained. In this manner, both univalves and bivalves may be conveniently disposed. But, as many of the former are very small in size, it is often necessary to fix them on pieces of card, that they may be preserved, and rendered easier of inspection. Perhaps the best mode of keeping these small shells, even the microscopic species, is to have a cabinet with slips of wood made to slide horizontally. These slips may be from one to three inches in breadth, and covered with white paper. Upon the middle of these the shells are fixed, with a solution of gum arabic and a little sugar, and the name marked on the edge. In many cases, when the shells are very minute, a narrow stripe of coloured paper may be fixed along the middle of the slip, to which the shells are to be attached. When neighbouring species are thus brought together, they can be easily examined with a lens. As a convenient and neat and useful method of keeping the smaller univalves, the writer of this article can recommend it from experience. It may be used with equal advantage by the botanist to preserve the smaller Lichens.

About the end of the sixteenth century, many individuals began to form collections of testaceous bodies. The first museum of this kind, of any consequence, was begun by Benedict Ceruto, and afterwards augmented by Calceolari. An account of the specimens contained in it was published by Olivi, in 1555, and, in 1622, Chiocco published plates of the shells. After this period, in proportion as collections of testaceous bodies became numerous, vari-

ous works on shells made their appearance. These Conchology were not published for any scientific object, but merely to teach collectors the names of the different specimens in their museums. As works of this sort, we may mention the Historia Naturalis of Johnston—the Gazophylacium Naturæ of Petiver—the Amboinsche Rariteitkamer of Rumphius—and the Wondertoonel der Nature of Vincent. Nay, to this list we might add many modern works, which are termed Systems of Conchology.

From the labours of this class of Conchologists the science has derived many important advantages. A taste for the study has been widely extended; the shells of distant countries and shores have been brought together; and numerous engravings of these bodies have been published. In this manner, the labours of the man of science have been greatly facilitated, and our knowledge of nature enlarged.—But it is time that we pass from the consideration of testaceous bodies, as objects of utility and amusement, to attend to the different methods which have been employed in their scientific arrangement.

Testaceous Bodies, considered as Objects of Scientific Arrangement.

Naturalists have pursued a variety of plans in their examination of this department of zoology, and have presented us with systems of arrangement founded on very different principles. Some Conchologists have attended solely to the form and structure of the shell, and have overlooked the organization of the animal inhabitant. A few have made the habits of the animal the groundwork of their systems. Others have passed over the appearances which the shells exhibit, and have confined their attention exclusively to the form and structure of the contained animal. Lastly, there have been a few who, embracing all the circumstances connected with the shell, the animal, and its habits, have constructed systems at once natural and convenient. In the following sections we propose to consider these four classes into which Conchologists may be divided.

SECTION I.—Systems constructed from Circumstances connected with the Characters of the Shell.

The arrangement of testaceous bodies according to their forms, is unquestionably the most obvious and the most ancient method. It was first employed by Aristotle, the father of Natural History, and even to the present day, its admirers are warm in its praise. It is with great propriety termed the artificial method, because the characters employed have no relation to any of the functions of animal life.

The Philosopher whose name we have now mentioned, had the merit of forming the divisions of Murex, or univalves, and Alvæ, or bivalves. He separated the turbinated univalves from such as have but an imperfect spire, and formed many genera, or rather families, which still retain the names which he imposed.

The science of Conchology made little progress for many ages after Aristotle had published his method of arrangement. Indeed, the first work of this class which merits attention, is the Dictionarium Ostracologicum of Major, which was published in

Conchology. 1675. To him we are indebted for the threefold division of shells into univalves, bivalves, and multivalves, and for an explanation of the terms then employed by Conchologists.

In the same career, but with more brilliant success, Langius followed, and, in 1722, published his Methodus nova Testacea Marina in suas Classes, Genera et Species distribuendi. The following character is given of this work by the intelligent and industrious authors of the Historical Account of Testaceological writers. (Linn. Trans. Vol. VII. p. 156.) "After having noticed a multitude of mere descriptors, we now come to an author who is not undeserving of the title of a scientific one, and whose system, so far as marine testacea are concerned (and of these alone he treats), certainly glances at the great clue to simplicity, which was afterwards so successfully and admirably seized by the great reformer of natural history in general." But Langius deserves more praise than is here bestowed upon him. Before his system appeared, the characters of the genera depended principally on the outline, and were of uncertain application. He remedied the defect, by directing the attention of Conchologists to the form of the mouth in univalves, and to the structure of the hinge in bivalves. Among the former, he constituted subdivisions of those ore superius aperto, ore superius in canaliculum abeunte, and ore superius clauso. Among the latter, the circumstance did not escape him, that some of these shells are equivalve, others inequivalve; some equilateral, others inequilateral. Hence he may be considered as the founder of the inferior divisions of the artificial method, and as having furnished, to modern Conchologists, many useful hints, of which they have availed themselves, without, however, acknowledging their origin.

Another important improvement was effected by Breynius in his Dissertatio Physica de Polythalamis, 1732, 4to. This consisted in separating from the ordinary univalves, such shells as possess a cavity divided by partitions into several compartments, and in forming them into a division, which he termed Polythalamium. These shells are now called Multilocular.

The system of Tournefort, which was published by Gualtieri, in his Index Testarum Conchyliorum quæ adseruantur in Musæo Nicolai Gualtieri, Philosophi et Medici, Florentini, 1742, well deserves an attentive perusal. In his observations on the bivalves, he drew the attention of Conchologists to an important character, and one of easy application, having observed that, in some genera, the valves do not close or unite all round, but that, at certain places, the shell remains in part open. Such shells, in modern language, are said to gape.

The system of the celebrated Linnæus, which ought now to be mentioned, is too well known in this country to deserve particular notice. In many of the other departments of Zoology he effected the most important alterations; but his attempts to reform the science of Conchology, were far from being equally successful. To the subject he never was much attached, nor does he appear to have availed himself sufficiently of the labours of those authors

whom we have mentioned, and of others who preceded him. The primary divisions which he employed, were those which Major had established, and his genera, with a few exceptions, were those in common use. His merit as a Conchologist rests entirely on the accurately defined terms,—the concise specific characters,—and the convenient trivial names which he employed and introduced. The particular consideration of the Linnæan genera, and the subsequent changes which have been introduced into them, will form the subject of a separate section.

For some time after the publication of the Systema Naturæ, the illustrious Swede enjoyed a very dangerous reputation. All his arrangements were regarded as of such high authority, that it was considered impious to attempt to introduce any change; so that Conchology, according to the artificial method, remained a long time stationary. At last in France, a country which refused to submit to the fetters of the Linnæan school, several new systems were proposed, which had for their object the restoration of those well founded genera, which Linnæus, in his too great desire to simplify, had suppressed, and the accommodation of the divisions of the science to those new relations which a more extensive knowledge of species had discovered. In this number Bosc stands eminently conspicuous. In his work entitled Histoire Naturelle des Coquilles, des Vers et des Crustacés, and in the conchological articles of the Dictionnaire d'Histoire Naturelle, he has favoured the world with a detail of his system, the outline of which we shall here present to our readers:

I. COQUILLES MULTIVALVES.

1. Les unes n'ont point de charnière.

2. Les autres en ont une.

II. COQUILLES BIVALVES.

I. Equivalves.

1. A charnière sans dents.

2. A charnière garnie des dents.

Venus
C. A quatre dents.
Bucarde
Meretrice
Lucine

D. A beaucoup de dents.
Nucule
Petoncle
Arche
Cucullee

In this system which we have exhibited, the ar-

rangement is more methodical, and the genera are Conchology more definite, than in the Linnaean system. It unquestionably holds the first rank in the modern artificial methods.

There is a class of writers whose labours deserve some notice in this place. We allude to those who have devoted their attention to the very minute shells, so common among the sand on every sea-coast. These are too small to be examined by the naked eye, and from the instrument employed in their investigation, they are usually termed Microscopic shells. Plancus, in his work, De Conchis Ariminensibus minus notis, published in 1739, may be considered as the first who drew the attention of Conchologists to these nearly invisible objects. J. F. Hoffman, in his Dissertatiuncula de Cornu Ammonis nativo Littoris Bergensis in Norvegia, published in the Transactions of the Electoral Academy of Mentz, 1757, and in his essay de Tubulis Vermicularibus Cornu Ammonis referentibus, ibid. 1761, made us acquainted with various species of minute nautili produced on the northern shores. Nor did those discoveries fail to excite interest in this country. Boys and Walker devoted their attention to the subject, and gave to the world the result of their labours, in a thin quarto, entitled Testacea Minuta variara nuperrime detecta in arena littoris Sandvicensis, London, 1784. Other observers, equally ardent and successful, have increased our knowledge of the forms of these minute bodies, particularly Soldani, who, in his Testaceographia ac Zoophytographia parva et microscopica, 1789 and 1795, exhibited many figures of the minute shells of Portoferrara, &c. The late Mr Adams described the minute species which he observed on the coast of Pembrokeshire, in the third and fifth volumes of the Transactions of the Linnaean Society of London, and other species of British growth have been investigated by the author of Testacea Britannica. We shall close this list with noticing the Testacea Microscopica aliaque minuta ex generibus Argonauta et Nautilus ad Naturam Picta et Descripta, Vienna, 1798. It is the joint production of L. A. Fichel and J. P. C. A. Moll, and merits an attentive perusal.

We are aware that such microscopic investigations are regarded by some Conchologists as useless, so that the minute species are excluded from their systems. But it is surely a strange method of proceeding in natural history, to judge of the merits or importance of species from their size. It is true that we are still ignorant of the inhabitants of those shells, and may long continue to be so; but our present knowledge of these has enabled us to fill up many blanks, to preserve some new relations, and even to draw some important conclusions.

That this sort of inquiry has in many instances been injudiciously conducted, all who are acquainted with the subject must admit. Due care has not been taken to distinguish these minute testacea from the fry of the larger shells, so that the number of species has been very injudiciously multiplied. These remarks apply to several figures of Walker, and to a still greater number of those of Adams.

Systems founded on the Habits of the Animal.

The authors of the preceding class have laboured to bring to perfection the artificial system of Conchology, and have formed their arbitrary characters, independent of the habits of life of the contained animal. But the naturalists whom we have now to consider, have traced these animals to their lurking places, and arranged them according to the situation in which they reside, instead of the forms which they exhibit.

At the head of this class of Conchologists Dr Martin Lister stands preeminently conspicuous. His great work, entitled Historia sive Synopsis Methodica Conchyliorum, was begun in 1685, and completed in 1692. It will long remain a monument of the extensive information and unwearied diligence of its author. The following synoptical view of the work will enable our readers to comprehend its plan; the original should be consulted with care.

Lib. i. De Cochleis terrestribus.

Pars 1. De Buccinis terrestribus.

Pars 2. Cochleæ nudæ terrestres Limacæ quibusdam dictæ.

Lib. ii. De Turbinibus et bivalvibus aquæ dulcis.

Pars 1. De Turbinibus.

Pars 2. De Testaceis bivalvibus fluviatilibus.

Lib. iii. De Testaceis bivalvibus marinis.

Pars 1. De Testaceis bivalvibus, imparibus testis.

Pars 2. De Testaceis bivalvibus, paribus testis.

Pars 3. De Testaceis multivalvibus.

Lib. iv. De Buccinis marinis quibus etiam vermiculi, dentalia et patellæ numerantur.

The plan followed by Sir Robert Sibbald in his Scotia Illustrata is somewhat different from that of Lister. He divides the Testacea into two classes, land and water shells, and the latter class he subdivides into fluviatile and marine. His inferior divisions are destitute of precision, and the number of his species limited.

The system of D'Argenville, which was so much esteemed and so long followed in France, is essentially the same with that of Lister in the higher divisions. The plan is indeed so simple, and in appearance so natural, that it has met with many admirers. It has even been useful in encouraging naturalists to study particular departments of the science, when they were prevented by their situation from devoting their attention to the whole. It is probably to this circumstance that we are indebted to Schröter for his observations on the land shells in the neighbourhood of Thangelstadt, and on the river shells of Thuringia.

The preceding arrangements, formed according to the situations in which the animals reside, and not according to their external coverings, may be considered as the first attempts at a natural method in Conchology. They serve as an introduction to a new class of authors, whose views may be considered

as of a higher order, and to whose labours we shall devote our attention in the following section.

Conchology.

SECTION III. Systems constructed from Circumstances connected with the Form and Structure of the contained Animal.

The first attempt, of any consequence, to arrange testaceous animals according to the soft parts of their bodies, was made by Adanson, in his Histoire Naturelle du Senegal, published at Paris in 1757. In this system, the ancient classes of Univalves, Bivalves, and Multivalves, are employed under the titles les Limaçons, les Conques, and les Conques Multivalves.

CLASSE I. Les Limaçons.

Sect. I. Les Limaçons Univalves.

Fam. 1. Les limaçons univalves qui n'ont ni yeux ni cornes.

Fam. 2. Les limaçons univalves qui ont deux cornes, et les yeux placés à leur racine et sur leur côté interne.

Fam. 3. Les limaçons univalves qui ont quatre cornes, dont les deux extérieur portent les yeux sur le sommet.

Fam. 4. Les limaçons univalves, qui ont deux cornes et les yeux placés à leur racine, et sur le côté externe, ou pas derrière.

Fam. 5. Les limaçons univalves qui ont deux cornes et les yeux posés un peu au dessus de leur racine et sur leur côté externe.

Sect. II. Les Limaçons Operculés.

Fam. 1. Limaçons operculés qui ont deux cornes, avec un renflement, et qui portent les yeux ordinairement au dessus de leur racine, et à leur côté externe.

Fam. 2. Limaçons operculés qui ont deux cornes sans renflement, et les yeux placés à leur racine, et sur leur côté externe.

Fam. 3. Limaçons operculés qui ont quatre cornes, dont les deux extérieur portent les yeux sur leur sommet.

CLASSE II. Les Conques Bivalves.

Fam. 1. Les conques bivalves qui ont les deux lobes du manteau séparés dans tout leur contour.

Fam. 2. Les conques bivalves dont les deux lobes du manteau forment trois ouvertures sans aucun tuyau.

Fam. 3. Les conques bivalves dont les deux lobes du manteau forment trois ouvertures, dont deux prennent la figure d'un tuyau assez long.

The presence or absence of an operculum or lid, gives rise, in this system, to a division of the univalves into two sections, and the families are established from circumstances connected with the number of the tentacula, and the number and position of the eyes. The families among the bivalves, are arranged according to the structure of their cloak or external covering. In the class of multivalves, which we have omitted in the table, the characters are taken from the form and structure of the shell.

The work of Geoffroy, entitled, Traité sommaire

Conchology. des Coquilles tant fluviales que terrestres, qui se trouvent aux environs de Paris, 1767, is constructed upon the principles of Adanson. Here, however, the objects were not sufficiently numerous to admit of all the subdivisions of that author, but he has made the form of the animal subservient to the construction of generic characters.

After these attempts to classify the animals which inhabit shells had been made in France, the celebrated Zoologist of Denmark, O. F. Müller, turned his attention to the same subject. In the Zoologia Danica, which contains his digested views of the subject, he employs, in the construction of his genera of univalves, the characters first used by Adanson; but among the bivalves, besides the form of the tubes or syphon, he notices the construction of the branchiae and the presence or absence of a foot.

To our knowledge of the animals which inhabit bivalves, Poli, in his History of the Shells of the Two Sicilies, made very important additions. In the construction of his families, which are six in number, he employs merely the characters furnished by the syphon and foot. In the first family the animal has two syphons and a foot; in the second, there is only one syphon and a foot; in the third, a syphon and no feet; in the fourth there is an abdominal syphon and no feet; in the fifth there is a foot but no syphon; while, in the sixth, neither foot nor syphon can be discovered. In the formation of his genera, Poli takes advantage of the various forms of the cloak and the branchiae.

To the celebrated Cuvier the Conchologist is also under the greatest obligations. By applying his vast knowledge of anatomy to the examination of the molluscous animals, he has unfolded many new conformations of parts, and exhibited many unlooked for relations. The vast collection of objects, the spoils of all the museums of the Continent, which Paris once possessed, lay open to his inspection, and his industry appears to have been equal to the harvest which invited him to labour.

In his first attempts to classify the molluscous animals, as contained in his Tableau Élémentaire de l'Histoire Naturelle des Animaux (1798), and his Léçons d'Anatomie comparée (1808-1805), he employed chiefly the characters which the preceding writers had developed, in his inferior divisions; but in his primary distinctions, he distributed the mollusca into three classes: Cephalopoda, having the head covered with tentacula, serving as feet: Gasteropoda, with the head free, the animal crawling on the belly: and Acephala, having no distinct head.

Some years after the appearance of this classification, Cuvier directed more of his attention to the internal structure of the mollusca, and, by means of accurate dissections, obtained a more intimate acquaintance with the organs and functions of these animals than any of his predecessors had acquired. The information which he thus gained, was communicated to the public at different periods, in the well known publication Annales du Museum d'Histoire Naturelle de Paris. These papers, with some additional observations, were at last published in a separate form, under the title Mémoires pour servir à l'Histoire et à l'Anatomie des Mollusques, Paris, 1816.

In the following year he published Le Règne Animal, Conchology distribue d'après son organisation, in which he arranged the mollusca according to his peculiar views, from characters drawn exclusively from the animal.

He divides the mollusca into six classes, which he terms Cephalopoda, Pteropoda, Gasteropoda, Acephala, Brachiopoda, and Cirripoda.

In the class CEPHALOPODA the body is in the form of a sack, open above, containing the branchiae, with a distinct head, surrounded by fleshy elongations or arms, adapted for moving the body or seizing prey. Into this class, along with the Sepia of Linnaeus, Cuvier has inserted the multilocular shells of his genus Nautilus, and the genus Argonauta. But it is to be feared, that our knowledge of the testaceous mollusca which inhabit the numerous multilocular shells, is too limited to enable us to assign them their true place in a natural arrangement of animals.

In the second class, termed PTEROPODA, the body is closed, the head is destitute of the long fleshy arms which distinguish the animals of the preceding division; two fin-like membranes, situated on the sides of the neck, and on which the branchial tissue is in general spread, serve as organs of motion. There is only one shell belonging to this class, viz. the Anomia tridentata of Forskaehl, now forming a part of the genus Hyalina.

The third class, which includes a great number of naked and testaceous mollusca, and to which Cuvier gives the name GASTEROPODA, from the circumstance of the belly being formed for crawling, has been subdivided into seven orders, from circumstances connected with the organs of respiration.

The first and second orders, Nudibranches and Inferobranches, consist almost entirely of genera formed from the animals which Linnaeus and many others included in the genus Doris. They are naked mollusca, and are likewise destitute of any internal testaceous plate. The third order, termed Tectibranches, contain animals whose branchiae, like small leaves more or less divided, are situated on the right side, or upon the back. The animals of this division possess a shell, but it is in general placed beneath the common integuments, such as the genus Aplysia and several species of the genus Bulla. In the fourth order, termed Pulmones, which breathe air, he has constituted two divisions, the terrestrial and the aquatic. The animals of the former live on land, and were included by Linnaeus in his genera Limax and Turbo. They are the land shells of most authors. Those of the division, termed aquatic, live in the water, but require, at intervals, to come to the surface to obtain fresh air. They constitute, with a few exceptions, the fresh water shells of naturalists. The Pectinibranches form the fifth order, and are distinguished by the branchiae, which are like leaves or threads placed parallel in one, two, or three lines, on the surface of the pulmonary cavity. It includes the whole of the marine species of the Linnaean genera of turbinate univalves. Into this order Cuvier, from the consideration of other characters, has inserted the genus Cyclostoma, which, according to the characters indicated by the respiratory organs, belongs to the Pulmones.

Conchology. In the sixth order, termed Scutibranches, the branchiæ are similar to those of the preceding order, but the sexes are united, each individual being capable of impregnating or being impregnated. The shells in general are cup-shaped, and destitute of a lid. It includes the genus Halyotis, and many species of the old genus Patella. In the last order, called Cyclobranches, the branchiæ appear in the form of small leaves or pyramids strung round the under margin of the cloak. They enjoy a hermaphroditism similar to those of the preceding order. The species of the genus Patella which are allied to the vulgata, and the genus Chiton, are included in this order.

In the fourth class, or ACEPHALA, he includes the bivalve shells, distributing them into families, from characters nearly similar to those which we have pointed out as having been previously employed by Poli.

The fifth class, termed BRACHIOPODA, contains animals, resembling those of the preceding class in having a cloak of two lobes, but these are always open. The branchiæ consist of small leaves placed on the inner margin of each lobe. In place of a foot they have two retractile fleshy arms, which are extensible. This class includes the Patella unguis of Linnæus, the genus Terebratula and the Patella anomala of Müller.

The class Cirripoda, distinguished by the articulated filaments with which the animals are furnished, contains the species of the genus Lepas of Linnæus. The shells belonging to the Linnæan genera Serpula and Dentalium, are transferred to the class termed Annelides.

This system of the molluscous animals is unquestionably the most perfect of all those which have been published. But, with all its excellence, we must inform the reader, that many species, nay, whole genera, have their places assigned them in this natural method, merely because the shells occupied a similar position in the artificial system, the form of the inhabitants being unknown.

SECTION IV.—Mixed Systems.

Mixed Systems. In this section, we shall confine our remarks to the only system of this kind of any consequence which has hitherto appeared, and which is the production of Lamarck, one of the most celebrated French zoologists of the present day. The Système des Animaux sans Vertèbres, Paris, 1801, of this author, embraces the whole range of animals included in the classes Insecta and Vermes of Linnæus. Where treating of the Mollusca he divides them into two orders. The first, termed Cephalous, from possessing a head, includes the univalves. The second, termed Acephalous, from the absence of a head, includes the bivalves. Instead of giving the outline of Lamarck's system as published in the work now mentioned, we propose rather to present the reader with the abridgment of his method, as contained in his Extrait du Cours de Zoologie, Paris, 1812; but we anxiously look for the completion of the great work, in which he is at present engaged, Histoire Naturelle des Animaux sans Vertèbres, where we hope to see this system rendered still more precise and useful. It is necessary to mention, that the animals are arranged

according to the perfection of their organs, beginning with the most simple. Conchology.

I. ACEPHALES TESTACES.

Ils sont enfermés dans une coquille bivalve, qui s'ouvre et s'articule en charnière.

A. Acéphalés monomyaïres, leur coquille offre intérieurement une impression musculaire subcentrale.

a. Acéphalés ayant deux bras opposés, ciliés, et qui se veulent en spirale en rentrant dans la coquille.

1. Les Brachiopodes.

b. Acéphalés sans bras, ne se fixant point par un byssus.

1. Les Ostracées.

c. Acéphalés ayant la plupart un pied propre à filer, et se fixant par un byssus.

1. Les Byssifères.

B. Acéphalés dimyaïres, leur coquille offre interieurement deux impressions musculaires séparées et laterales.

a. Coquille inequivalve.

1. Les Camacées.

b. Coquille equivalve.

* Acéphalés lamellipédés; leur pied est aplati et lamelliforme. Ligament extérieur, la coquille non baillante aux extrémités laterales.

† Aucune dent, ou une seule dent sur chaque valve les crochets écorchés.

Les Nayades. (Coq. d'eau douce.)

†† Charnière multidentée.

Les Arcacées.

††† Dents cardinales, grossières, et irrégulières.

Les Cardiacées.

** Acephales crassipedes, leur pied est épais, souvent subcylindrique. Le ligament intérieur, ou la coquille baillante aux extrémités laterales.

† Ligament intérieur dans une fossette.

†† Ligament intérieur, sur une dent clargie.

††† Ligament extérieur. Coquille sabulicoles, non terebrantes.

†††† Ligament extérieur. Coq. terebrantes, sans pièces accessoires.

††††† Ligament extérieur ou inconnu. Coquilles terebrantes, avec une ou plusieurs pièces accessoires, distinct des valves.

A. Branchies extérieur, placées sous le rebord du manteau, et disposées en série longitudinale entre ce rebord et celui du pied. Elles ne respirent que l'eau.

B. Branchies extérieures, composées d'une ou deux pièces placées au-dessus du cou, sous le manteau. Elles ne respirent que l'eau.

C. Branchies cachées ou couvertes, mais en saillie dans un cavité particulière. Elles ne respirent que l'eau.

D. Branchies cachées dans un cavité particulière, et étendues sans saillie sur les parois de la cavité. Elles ne respirent que l'air libre.

A. Sans siphon saillant, et respirant en général par un trou. Coq. à ouverture entière, n'ayant à sa base ni canal ni véritable échancrure.

a. Ne respirant que l'air. Leur branchies sont étendues sur les parois de la cavité branchiale, sans y former de saillie.

• Tentacules cylindriques : coquille terrestre, avec ou sans opercule.

** Tentacules aplatis : coquille d'eau douce toujours sans opercule, et dont l'animal vient respirer l'air à la surface de l'eau.

b. Ne respirant que l'eau. Leurs branchies forment des parties saillantes dans la cavité branchiale. Les uns sont fluviatiles, les autres marine.

• Coquille fluviatile, dont le bord gauche de l'ouverture n'imité pas une demi-cloison.

† Coquille operculée dont les bord de l'ouverture sont disunis.

†† Coquille operculée, dont les bord de l'ouverture sont réunis.

** Coquilles fluviatiles ou marine, dont le bord gauche de l'ouverture imite une demi-cloison. Point de columelle; un opercule.

*** Coquilles marine, dont le bord gauche de l'ouverture n'imité pas une demi-cloison.

† Coquille flottante.

Janthine.

†† Des plis à la columelle.

††† Ouverture obronde à bords reunis.

†††† Ouverture evasée, à bord disunis.

††††† Ouverture non evasée, à bord disunis.

B. A. Siphon saillant. Ils sont tous marines, carnassiers, et ne respirent que l'eau, qui parvient aux branchies par un siphon. Ouverture de la coquille, soit canaliculée, soit echancrée ou versante à sa base.

a. Un canal plus ou moins long à sa base de la coquille; le bord droit de l'ouverture ne changeant point de forme avec l'âge.

b. Un canal plus ou moins long à la base de la coquille; le bord droit de l'ouverture changeant de forme avec l'âge, et ayant un sinus inférieurment.

c. Canal nul ou très court. Uni echancrurée oblique à la base de l'ouverture.

d. Point de canal à la base, mais une echancrurée plus ou moins grande. Des plis sur la columelle.

c. Point de canal: tour de spire larges, comprimées, et enroulées de l'axe de manière que le dernier recouvre presque entièrement les autres.

a. Coquille multiloculaire à cloisons simples: leurs cloisons simples sur les bords, n'offrent point des sutures decoupées et sinueuses, sur la paroi interne du test.

* Coquille droite ou presque droite, point de spirale.

** Coquille partiellement en spirale; le dernier tour se terminant en ligne droite.

*** Coquille semi-discoidale, à spire excentrique.

**** Coquille globuleuse, spheroidale ou ovale: à tours de spirale enveloppans, ou à loges reunies en tunique.

***** Coquille discoïde, à spire centrale, et à loges rayonnantes du centre à la circonference.

***** Coquille discoïde, à spire centrale, et à loges qui ne s'étendent pas du centre à la circonference.

b. Coquille multiloculaire à cloisons decoupées sur les bords. Les cloisons, sinueuses et lobées dans leur contour, se reunissent contre la paroi interne du test, et s'y articulent en sutures decoupées comme de feuilles de persil.

The authors of the first class of Conchologists which we have mentioned, employ exclusively the characters furnished by the shell, and scarcely deign to tell us that there is an animal attached to that shell. The authors of our third class are anxious to keep the shell out of view, and draw their distinctions from the animal; but they have failed in the attempt. In extreme cases, the characters of the shell are resorted to in the absence of distinctions furnished by the animal.

Lamark perceived the inconvenience of separating these two modes of examining molluscous animals, and fortunately formed a very natural combination. We shall give his character of the genus Patella, as a specimen of this mixed system.

Coquille univalve, non spirale, ovale, ou suborbiculaire, en bouclier ou en bonnet, concave et simple en dessous, entière à son sommet, et sans fissure à son bord.

Patellier: Gastropode à tête tronquée obliquement, munie de deux tentacules pointues. Les yeux à la base extérieure des tentacules. Les branchies placées autour du corps, sous le rebord du manteau.

In this manner the generic character is dependent equally on the shell and the contained animal, and that genus in a system is consequently not sufficiently established in which both these characters are not included. How many genera are in this imperfect state! Were the same plan followed in the description of species, everything we could wish for would be detailed; and our knowledge of the forms of molluscous bodies would approach to perfection. How much is it to be wished, that this plan of Lamark's were generally adopted in this country! Conchology would assume a new aspect, and the number of its votaries would rapidly increase.

The reader will have perceived, in the course of the hasty review of those systems which we have enumerated, that we have refrained from making any remarks on their comparative excellence. This deficiency we now propose to supply in the following observations.

The authors that have arranged testaceous bodies, without reference to the animals that reside in them, appear to have mistaken the house for the inhabitant, and the thing formed for the being that produced it. They have torn asunder objects which are closely related, and united others which differ in structure and economy. These are necessary consequences of an artificial system, and they become

more obvious in proportion as we descend in the Conchology scale of being.

The examination of shells, according to this method, may be viewed as the study of the osteology of the Mollusca. It has not for its object the investigation of living matter, but of dry bones. Nor has it any of those advantages which result from the study of the osteology of the vertebral animals. A knowledge of the bones of these animals enables us to ascertain many of their primary functions, the nature and extent of their powers of motion, and even the food on which they subsist. But our knowledge of shells merely, enables us not to say, whether the animal can crawl or swim; whether it feeds on plants or animals. The reason is obvious. All the muscles inserted upon the shell are either mere organs of adhesion, or destined to open and shut the valves. None of those muscles connected with any of the primary organs have any connection with the shell. That the shell furnishes several important characters, we readily grant; but we are here reasoning against the propriety of attending to the shell, to the exclusion of the animal, and, to this extent, our reasoning appears to be conclusive.

We are aware, that, in the other departments of natural history, the appearances which the external parts of an animal exhibit are constantly employed in the construction of orders and genera, and all the intermediate divisions. Thus, for example, the bill, feet, and feathers of birds, furnish the characters by which they are arranged in the system. Here, however, it must be observed, that the combined information yielded by these parts, makes us acquainted with the habits and organization of a bird. By means of these we can judge, and with certainty, not merely of its internal structure, but the places which it frequents, and the food which it consumes. Hence these characters may be applied with equal propriety in an artificial as in a natural method. But what opinion would we form of that Ornithologist, who could readily inform us that the cornorant has fourteen tail feathers, and the shag only twelve, but who was ignorant of the haunts of these birds, their food, and the number of their young. We might prize him as a companion in surveying a museum, but he is alike a stranger to science and nature.

Nor can we feel more respect for the student of mere shells. He may be able to tell us the number of whorls in a spiral univalve, or the form of the hinge in a bivalve; but if he knows not the nature of the organs of respiration, digestion, and reproduction of the animal to which the shell belongs, and contentedly remains in this ignorance, he has yet to learn the value of method in natural history. He cherishes with mistaken fondness the maxim of Linnaeus, "Nomina nosse oportet qui rem scire velit," while he overlooks a more important object, expressed in the motto of the Linnaean Society, "Naturæ discere mores."

These remarks apply to the conchological labours of Linnaeus and his followers, who have devoted their whole attention to the arrangement of the shells, without attending to the animals. We know that

Conchology. some of the admirers of the Swedish naturalist presume to say, "But our great author was not wholly inattentive to the creatures for which the beautiful and endlessly diversified receptacles that he had characterized were designed. Among the generic marks was included the name of the molluscous inhabitant; or, where the animal differed from any which had a place in other parts of his system, he described it at length." (Linn. Trans. Vol. VII. 175.) Now, to what does all this attention of Linnaeus amount? In all the species which he has described, he has only noticed the animals of four of these, and in a very slight manner; and, with regard to the name of the molluscous inhabitant which he included in his generic marks, we hesitate not to say, that by this union he has betrayed carelessness. To many British ears these terms may sound harsh, but the proof of their correct application in the present instance will be abundantly evident, if we examine the references to the animals of a few of his genera. The genus CHITON is thus characterized—"Animal Doris. Testæ plures, longitudinali, et gestæ, dorso incumbentes." Are we not led to conclude from this character, that the animals of the Chiton exactly resemble the animals of the Doris genus, with the addition of the shells? If this be the case, how artificial is that system which places these two genera in separate orders! Upon turning, however, to the genus Doris among his vermes mollusca, we find the following characters assigned to it—"Corpus repens, oblongum, subtus planum. Os antice subtus. Anus postice, supra cinctus ciliis. Tentacula duo, supra corpus antice intra foramina retractilia." Now, the fine fringes around the anus of the Doris, which are the branchiæ of the animal, and form the essential character of the genus, are not to be found in the animals of the Chiton, whose branchiæ are in the form of little leaves placed along the margin of the body, and the anus is a simple pore.

According to the generic character of the Mya, the animal is an Ascidia, with the appendage of a shell. Upon turning to the genus Ascidia, we find it said "Corpus fixum, teretiusculum, vaginans. Aperturæ binæ, ad summitatem; altera humiliore." To prove the impropriety of referring the animal of the Mya to the genus Ascidia, we shall only mention, that the former has a foot, and possesses a locomotive power,—the latter has no foot, remains immovably attached for life upon the substance to which it first adhered, and depends on the accidental bounty of the waves for all its nourishment.

The animals of nearly all the univalves are represented as belonging to the genus Limax. But, with the exception of the restricted genus Helix and Bulimus, the animals of the univalves are all generically different from the Limax. Their tentacula are generally two in number, with the eyes at the base; while the tentacula are four in the Limax, with the eyes at the tips of the two longest. These examples will suffice to establish a truth so palpably obvious.

The principal objection against this system of employing the shell, to the exclusion of the animal, arises from the fact, that nature has not drawn a line of distinction between the mollusca and the testacea.

Thus, many of the vermes mollusca of Linnaeus include shells in their bodies, as the Aplysia; and many of his vermes testacea likewise are soft on the outside, the shell being enclosed by the integuments, as the Helix Haliotoidea.

We have another objection to this artificial system, and one which we consider of great force; that, wherever it prevails, the form and habits of the animal are overlooked. How fully is this truth illustrated in the works of the Testaceologists of this country! We might examine all their writings, from the Pinax of Merret to the Descriptive Catalogue of Maton and Racket, including the works of Pennant, Berkenhout, Da Costa, and Donovan, and learn little more, besides the habitat, than that to every shell there is an animal attached. Of this charge the names of Lister and Montagu stand acquitted. The former has given us several good dissections, and the latter minute descriptions, of the testaceous animals.

While, in the preceding remarks, we have objected to all arrangements taken exclusively from the characters of the shell, we also disapprove of those systems founded exclusively on the characters of the animal. By the former class of methodists, the simplicity of nature is sacrificed to their peculiar views, and, by the latter, practical utility is disregarded. Devoting their whole attention to the animal, the latter Conchologists have overlooked the house in which it resides,—the roof which shelters it from the blast,—and the walls which guard it from its foes. The former Conchologists possessed very limited views of nature, and erected systems obviously artificial. To the systems of the latter, the same objections will apply. Thus, for example, among the univalves of Adanson, the families are formed from the position of the eyes chiefly. That the black points which we witness at the tips or the base of the tentacula are actually eyes, we readily admit; but what influence has these eyes on the habits of the animal? or rather, does a change of position of these organs occasion a corresponding change in the habits of the animal? Unless this is answered in the affirmative, we must consider such characters as equally artificial with any employed by Linnaeus or his followers, since they have no relation to any of the primary functions of life.

The employment of characters taken exclusively from the animal is attended with so many practical difficulties, that it never can be introduced into general practice. If we find a shell thrown ashore, the animal may be dead, or it may refuse for a time to display its organs, and prevent us from arriving at its name and history. This defect, however, is partly remedied when we can call to our aid the characters furnished by the shell.

Another objection against this method arises from the well known difficulties attending the preservation of the molluscous animals. To dry them, destroys their form and texture; to inject them, is impracticable; and when put into spirits of wine, they generally appear a shrivelled mass. But the coverings of these animals are durable, and, since they form a part of the animal,—since they are produced at first along with it, increase by the addition of new matter from its body, and continue attached to it for life,—we

Conchology must condemn any classification from which the shell is excluded.

From these remarks, it will be obvious, that we consider the mixed system as the most natural and the most useful. It possesses all the advantages to which the other systems lay claim, while it is free from their defects. It withdraws part of our attention from the shell, because it is destitute of peculiar vessels, and possesses no vital energy, to fix it on those organs of the animal which are subservient to its existence. It leads us to examine the whole animal, instead of certain parts of it merely, and has a tendency to excite us to become acquainted with the manners of a tribe, from which, imperfect and artificial systems have hitherto withdrawn our attention.

It is of the utmost importance in the formation of any arrangement of natural bodies, to have an exact idea of the relative value of the characters used, and of their true subordination. This is a subject of vast moment, and too little attended to by naturalists. We do not here consider that character as of the highest kind, which is the most general, but that which has the greatest influence over the faculties and instincts of the animal. Had this subject been studied with greater care, the science of Conchology would, at this period, have been in a more flourishing condition. To ascertain, in some degree, this subordination of character, is the object of the following observations.

The division of the testaceous mollusca into three orders, as adopted by Linnæus, is confessedly artificial. The Multivalvia of that author possess no characters in common, neither can they boast of a general resemblance. The first genus, Chiton, consists of animals which belong to the cephalous and gastropodous mollusca. The animals of the genus Lepas approach more nearly to the crustacea than the mollusca; while the animals, inhabiting the genus Pholas, belong to the accephalous mollusca, and are closely connected with the Myæ and Solenes. The shells of the first genus are merely calcareous scales, arranged transversely on the back of the animal. The shells of the second genus are variously articulated, fixed, and either sessile or pedunculated. The shells of the third genus are bivalves, with a few accessory calcareous plates. It is to be hoped that modern Conchologists will avoid so incongruous a combination.

The two remaining divisions of Linnæus, the bivalves and univalves, are not only obvious, but natural. They indicate the existence of certain forms peculiar to the animals whose shells are thus separated in the system. The univalve shells are inhabited by animals which possess a head, and whose organs of motion are either tentacula, situated on the head, or a foot spread over the belly, as in the slug. The animals of the bivalve shells, on the other hand, are destitute of a head; some of them have no locomotive power; and, in others, the organ of motion is a fleshy foot, which the animal can protrude at pleasure. These circumstances point out the connection which subsists between the organs of the animal, and the external forms of the shell; a connection which, in every system, ought to be carefully attended to.

It is somewhat difficult to point out, among the

univalves, the true subordination, or relative importance of the characters employed by Conchologists in describing them. We have much to learn of their anatomy, and hence we cannot with certainty point out the relation of the parts of the shells to the organs which those parts protect. The form and structure of the mouth, however, may be expected to furnish characters of the first-rate importance, and have always attracted the notice of the student of testaceous bodies. The very shape of the animal, together with its ordinary habits, must necessarily depend, in a great measure, on the form of the mouth.

In many genera, the mouth of the shell towards the base is produced, and terminates in a groove or beak. These univalves are termed canaliculated, and are readily distinguished from those whose mouth is entire. The differences in the form of the shell in these two divisions is an index of equally remarkable differences in the form of the animals. The canaliculated shells contain animals possessed of an elongated tube for the purposes of respiration, and this canal is destined for its reception and protection when expanded. The animals whose shells are destitute of this canal, are likewise destitute of this lengthened respiratory tube. Circumstances of this kind induce us to believe, that shells, agreeing in external form, in general, contain animals of a similar organization. We consider this division of the univalves into canaliculated and entire, as obvious and natural.

The next character, in point of importance, appears to depend on the direction of the revolutions of the spire. In general, when a spiral univalve is placed upon its base, or mouth, with its summit towards the observer, the mouth will open on the right side of its axis or pillar, and the whorls will be observed to revolve from right to left, beginning at the base, and ending at the summit. These shells are termed dextral. In a few shells, however, this order is reversed. The mouth occurs on the left side of the pillar in the above-mentioned position, and the whorls from the mouth to the summit revolve from left to right. Shells of this sort are termed sinistral, sometimes also heterostrophe or heteroclite, and are generally called by dealers unique.

In the dextral shells, the animals have the external openings of the rectum, penis, and uterus, on the right side of the body, and the heart on the left. In the sinistral shells, these organs are placed on the opposite sides. Thus the openings of the rectum and organs of generation are on the left side, while the heart is situated on the right. Here again we have an external character impressed on the shell, which indicates certain arrangements in the organs of the animals. We are aware that some Conchologists consider the sinistral shells as accidental varieties, and on that account regard the character which is indicated as of inferior importance. Bosc, indeed, says, "La cause de cette variation dans la direction des spires, vient des circonstances dans lesquelles s'est trouvé l'animal au moment de sa naissance, et d'un obstacle qu'il a trouvé lorsqu'il a voulu tourner sa tête du côté que la nature lui a indiqué." This explanation might have been received, had such changes

Conchology. in the direction of the whorls been confined to one individual or two, of particular species. But when we observe all the individuals of particular species, nay even of genera with their whorls thus invariably reversed, we are disposed to regard the occurrence as connected with the primary structure of the animal, and not as the result of accident. Besides, the viscera of the animal of a reversed shell are not placed in the same position in relation to its back or belly, as the animals of the dextral species. A simple change of direction in the spire, therefore, will not convert a dextral into a sinistral species, and the character must be considered as of a higher order than those employed for the separation of the species merely. We consider sinistral shells as belonging to distinct genera from those which are dextral, it being inexpedient to make use of the character for higher divisions.

Among many of the univalves, the animal is furnished with a lid, by means of which it can close up the entrance of the shell after it has withdrawn itself into the cavity. It is in general corneous, sometimes also calcareous. It is usually flat, and attached to the superior and posterior part of the foot of the animal. The shells which possess this lid are generally termed operculated shells. They must not be confounded with those land shells whose animals form a temporary covering to the mouth, previous to winter, for the purpose of protecting them from the vicissitudes of the weather. This, in the former, is permanent, in the latter deciduous; in the former it adheres to the animal; in the latter only to the margins of the mouth of the shell.

This character was first employed by Adanson in the construction of the second section of his class univalves, and has been more or less attended to by succeeding Conchologists. It is certainly a very general character, and at first sight might be supposed worthy of forming some of the higher divisions. It appears but rarely in the land shells, more frequently in fresh water shells, and generally in the marine species. It does not, as yet, appear to be connected with any peculiar organization, although it must influence to a certain extent the economy of the animal. Were we, however, to employ it in higher divisions than generic ones, some confusion would certainly arise. It would cause the separation of many genera which are nearly allied, and even divide several natural families. Thus, for example, among the porcellaneous shells, it would separate the olives from the cones, the former being destitute of an operculum, while the latter possess one. These two genera, however, belong to a natural family, the animals of both genera having a respiratory tube upon the head, and the eyes placed on the sides of the tentacula, instead of being situated, as in the other gasteropoda, on the tips or at the base. This circumstance is calculated to convince us of the necessity of caution in the admission of characters. These may at first appear to be of extensive occurrence, and well adapted for the formation of families, but unless they exercise some visible influence on the animal, they can never be employed with propriety in a natural system, however convenient they may be in an artificial arrangement. Oper-

culated shells may be considered as generically different from those which are destitute of that organ, without any injury to the natural method. It would even, in many instances, be convenient. Conchology.

Among univalve shells, considerable differences are observable in the shape and position of this cavity. In some this cavity is simply conical, while in others it is conico-tubular, either revolving horizontally round a centre, or spirally twisted upon an axis or pillar. These circumstances furnish characters of great importance in an artificial system, as by means of them all testaceous bodies may be arranged into two tribes, the one possessing a pillar, round which the tube of the shell is twisted, while the other is destitute of any pillar. The former have been termed Stulidia, the latter Astulidia. As a natural character, however, these distinctions are of inferior importance, and, if employed, would occasion a separation between the genera Planorbis and Lymnaea, which are demonstrated by Cuvier to be nearly related. In the formation of genera, it may be employed with advantage, even in a natural system, aided by the structure of the pillar, and the direction of the whorl.

The last character which we have to notice while speaking of the univalves, depends on the circumstance of the cavity being entire, or divided into chambers, being unilocular or multilocular. In the multilocular testacea there are a number of transverse plates, in some species perforated, in others entire, which cross the cavity of the shell, and, in general, divide the external cavity, in which the animal resides, from the older and smaller ones, from which it has receded. In an artificial arrangement, such distinctions may be employed with advantage, even in the formation of the primary divisions, but we entertain doubts as to the propriety of using them in a strictly natural method. We are in a great measure ignorant of the animals which inhabit the multilocular shells, yet as far as our knowledge goes, we are induced to regard the distinction as merely conventional, and as unconnected with any peculiar order of organization. Such a division may be useful in the present state of the science, and may be permitted on that account; but in proportion as our knowledge of the mollusca advances, this distinction will be deemed inexpedient. Indeed, were this division adopted, the genera Argonauta and Nautilus would be torn from each other, although they are, by Cuvier and many others, regarded as members of a family of cephalopodous mollusca. The Nautilus lacustris of Lightfoot would, in that case, likewise be separated from the genus Planorbis, with which it is very closely allied. In the meantime, until our knowledge of the multilocular testacea arrives at a greater degree of perfection, such divisions may be employed as convenient, and of easy application.

The preceding remarks apply to those shells which belong to the cephalous mollusca. Among the bivalve shells, which belong to the accephalous mollusca, the characters which they exhibit are of very different degrees of importance. Here, as among the univalves, the appearance of the shell enables us to form an idea of the organization of the animal, so

Conchology, so that the characters thus furnished by the shell, may be safely employed in a natural system.

The bivalve shells, in general, possess the faculty of moving from one place to another, or of attaching themselves to rocks and stones, by means of temporary threads. These are termed free shells. But there are others which secrete at their birth a calcareous cement, which unites the shell to the rock or stone immovably for life. These last are known by the name of fixed shells. If we thus consider the difference in the economy of these two divisions of bivalves, we may reasonably expect to find corresponding differences in their organization. The free shells contain animals endowed with locomotion, and by consequence with feet. In few of the animals which inhabit fixed shells can a foot be observed. They are more simple in their organization than the free shells,—are destitute of absorbing or ejecting syphons, the place of these being supplied by holes in the duplicature of the cloak. This last distinction, however, is not peculiar to the fixed shells, although found in all of them.

Among the free shells, a very important circumstance occurs, which we have already noticed, viz. that some of these adhere to rocks and stones by means of temporary threads produced by the animal. They are termed byssefere. Independent of the utility of this power of producing threads of attachment, to the economy of the animals, the byssefere must possess at least three organs of which the other testaceous mollusca are destitute. The first of these is a gland for the secretion of the substance of which the threads are formed; the second, a foot so constructed as to be capable of spinning these threads and fixing them to the rocks or other bodies to which they are intended to adhere; and the third is a muscle in the animal to which the inner end of these threads may be attached, and which muscle, in general, has the power of contraction and elongation. This character, then, appears perhaps of the very highest order, so that, in a natural arrangement, we might divide the molluscous bivalves into such as spin threads of attachment, and such as do not. We must, however, confess, that the byssefere have scarcely any other subordinate characters in common, to warrant such an arrangement.

In general, the valves of which the shell consists close upon each other in such a manner as to leave no opening. In a few genera, however, the valves do not close upon each other at one end, and sometimes at both; the point of union being at one side or in the middle. The former are termed close shells, the latter gaping shells. The character of gaping, so very obvious in the shell, is an index of equally important distinctions which prevail in the animal. In the gapers, the syphons, or the absorbing and ejecting pipes, are two in number, and very long, and frequently united. The foot is contained in a sheath, from which it issues at the pleasure of the animal. Besides, the branchiae are always united, and equal in length to the tubes. This character appears, therefore, equally important as the former. It has hitherto been employed in the construction of specific characters merely, rarely of genera.

When the two valves are of the same size and

form, the shell is said to be equivalve; but when the Conchology, one valve differs from the other in these particulars, the shell is said to be inequivalve. This character, so obvious and so commodious, is not the index of any peculiar organization of the animal. If employed in the higher divisions, it would separate closely connected genera, and destroy some natural alliances. The inequivalves, however, are for the most part irregular in their growth. The molluscous inhabitants have no lengthened syphon nor foot.

When we examine the inner surface of bivalves, we observe some spots of a different colour and lustre from the general surface. These are the places to which the muscles adhered, which connected the animal with the shell, and are termed muscular impressions. They are either separate and lateral, subcentral, or simple, or composite. This character was long employed by Conchologists in their specific distinctions, and sometimes in the formation of the genera. It has of late been employed by Lamarck, as a character of the first importance in the division of the bivalves. He forms these shells into two sections, the first containing those shells which have the muscular impressions separate and lateral, and the second such as have only one subcentral, simple, or compound impression. However highly we respect the conchological labours of this naturalist, we cannot join with him in the present instance, and elevate a subordinate character to a primary rank. If, by muscular impressions, he means those marks impressed on the valves of the shells by the muscles which serve to close it, then his character is unconnected with any of the primary functions of the inhabitant. For is it of much consequence whether the valves be brought into contact by the action of one muscle or by the assistance of two? In so far, the character is evidently artificial, when the impressions of the adductor muscles only are employed. But he evidently uses the term in a more extensive sense, to refer to those impressions left on the shell by some of the other muscles by which the animal is attached to it. To the mere Conchologist, these marks are of a very uncertain import, and can never enable him to construct natural families, and the student of the mollusca will employ more important distinctions. If we are to take all the muscular impressions into account, the arrangement of Lamarck must undergo great alterations. Let us take the common mussel as an example. It is placed by the French Conchologist in the second section, as having only one muscular impression, although no less than four muscles adhere to each valve, destined for the performance of very different functions. The largest impression, which is situated near the obtuse end of the shell and towards the posterior margin, belongs to the adductor muscle, employed in closing the valves. Connected with this impression there is a tongue shaped mark, reaching nearly to the ligament. This mark is occasioned by one of the lateral muscles for supporting the byssus, and by one of the lateral muscles of the foot. The other muscle for supporting the byssus, is inserted under the teeth which occur at the beak. There is even another mark of adhesion on the margin of the shell, irregularly denticulated, oc-

Conchology caused by the fringed margin of the cloak, which is there united with the shell. This mark may be termed the marginal impression. To which of these marks then are we to attach the greatest importance? To the impression of the one adductor muscle, which is common to all shells,—to the marks of the muscle of the byssus, or to the indented mark of the fringed margin of the cloak. If we attend farther to Lamark's arrangement, we shall find the Camacea separated from the Ostreacea, although the two families possess numerous external and internal points of resemblance. We regard the muscular impressions as furnishing a convenient character for the construction of genera, and the discrimination of species, but it is not worthy to occupy so high a rank as Lamark has assigned to it.

As intimately connected with the muscular impressions, we may here notice the ligament. It is a horny elastic membrane, which serves to open the valves, when the adductor muscle relaxes. It is placed on the exterior margin in some shells, and is concealed in others. When external, it is stretched when the shell is closed, and when it is internal, it is compressed in similar circumstances. This character is very useful in the construction of genera, but it ought never to be employed in any of the higher divisions. It is not the index of any peculiar organization, neither does it serve to unite natural families. Lamark, without due consideration, regards it as next in importance to the muscular impressions.

The teeth of the hinge of bivalves, since the days of Langius, have been studied with care, and the characters which they furnish have been employed, both in artificial and natural arrangements, in the construction of the primary divisions. It would have been of some advantage to the science had Conchologists ascertained the use of the teeth, in the economy of the animal, before forming any divisions from their presence, absence, or position. They do not appear to be the index of any peculiar organization, neither can they be employed to bring together naturally allied families. The use of the adductor muscle is to close the shell; the ligament opens it; and the teeth of the hinge seem destined to modify and direct these movements. The characters furnished by these three parts of the shell, appear to be nearly of equal importance, and fit only to occupy a very subordinate place. Were the circumstances connected with the teeth of the hinge to become the foundation of the higher divisions, many natural families would be broken. Thus, the genus Anodonta, would be removed from the Unio, although they are both fluviatile, possess one long subulated foot, one syphon in the form of a hole, the summit of the cloak furnished with cirri, the branchiae in part reunited, viviparous, carrying the young in the branchiae. In short, it seems to be a character fit only for generic and specific distinctions.

Bivalve shells have often been divided into equilateral and inequilateral. These differences do not appear to be the signs of any peculiar character of the animal, or any of its functions. They must influence, to a certain extent, the relation between the different parts, but this influence is not sufficiently obvious. The character, thus furnished, is of an uncertain kind. It is influenced by the age of the

individual, and, therefore, can only be employed Conchology with caution in specific distinctions.

The last character of the bivalves, which we shall notice, is the power which some of them possess of piercing stones and wood for the purpose of forming to themselves a retreat. These are termed borers. It was supposed by many that the animal secreted a liquor with which it dissolved the bodies into which it penetrated, but the sagacious Reaumur soon ascertained that the boring was performed by means of a rotatory movement of the larger valves. M. Fleurieu-Bellevue states, that the calcareous stone, in which the Rupellaria lithophaga is found, is often discoloured in the immediate neighbourhood of its recess. This may arise from other secretions of the animal, or even from the stagnant sea water in the hole, and not from the action of the phosphoric acid, or any other solvent supposed to be employed by the animal. These would act equally on the shell as on the calcareous rock. But the borers are not confined to calcareous rocks, they also lodge in slate-clay, and other argillaceous strata. This is very often the case with the Pholades. But this character can never be extensively employed, as the same species which, at one time, may be found imbedded in stone, will be observed at another seated among the roots of sea-weed, or buried among gravel.

From the preceding remarks it will appear obvious, that there are many characters furnished by the shell, which give us indications of corresponding peculiarities in the structure of the animal, and on that account ought to be employed in every natural arrangement. These characters have this circumstance to recommend them, that they are obvious and permanent. The objects which furnish them can be preserved in our cabinets, and serve to perpetuate our recollection of the appearances which the more perishable parts have exhibited.

There is yet another class of characters to be considered, very variously rated by different authors. These characters are taken from the situation in which shells are found, whether on the land, in fresh water, or in the sea.

This mode of dividing testaceous bodies has not been sufficiently attended to by Conchologists, who have, in general, condemned the plan, as founded upon an improper principle, viz. the classification of animals from the places which they frequent, instead of the forms which they exhibit. Such a mode of arranging the higher divisions of the different classes we would readily censure; but when employed in the inferior subdivisions of the testacea, we regard it as an important and a natural character. We ask the true naturalist to say, Which is the most important character, the hinge having teeth or wanting, and the animal residing in fresh water or in the sea? We anticipate with confidence the preference which would be given to the latter, although the decision might provoke a sneer in a mere collector. Nature has evidently drawn a line of separation between the three tribes, which it is not difficult to perceive.

The terrestrial testacea are destined to live on vegetable matter. Their organs of respiration are suited to the medium in which they reside. Their organs of feeling are, in general, more numerous

Conchology. than those of the fluviatile or marine shells. The tentacula of the latter seldom exceed two, while in the land shells the tentacula are, in general, four in number. The eyes are likewise differently placed; in the aquatic testacea they are situated on the head, at the base of the tentacula; whereas the eyes in nearly all the terrestrial species are placed on the tips of these organs. We might also add, that no bivalve shells are found on the land,—they belong exclusively to fresh water and to the sea.

The fluviatile shells, though destined to reside in a different medium from the terrestrial, have their organs of respiration (according to Cuvier) nearly the same, and are, therefore, compelled to come occasionally to the surface to respire. They have, in general, two flat tentacula, with the eyes placed at the base. They may, in general, be distinguished from the marine kinds, by the superior thickness of their epidermis,—their corneous colour, and semitransparency.

The marine shells are the most numerous,—the most beautiful,—and the most highly prized of all the testacea. Many of the univalves of this tribe possess a lengthened respiratory tube, with a canal in the shell for its protection,—a circumstance not observed in the fluviatile testacea. There is one circumstance which at once points out the difference in structure between the fluviatile and marine testacea: The fluviatile cannot live in salt water, nor the marine in fresh water. This fact points out an arrangement in their organization to which Conchologists ought to pay attention.

These remarks are calculated to persuade Conchologists to attend to the character furnished by the habitation of shells. In the formation of genera, it ought to be respected; in the higher divisions it would be inconvenient. The carelessness of Linnaeus with regard to this character, is the principal reason why his genus Helix is such a confused and indigested mass. Were the distinction arising from habitation to be observed in the distribution of the testacea, no confusion could possibly take place. Some changes might be occasioned by it, but much practical difficulty would be avoided. Indeed, so useful is the distinction, that Conchologists, without avowing the propriety of the principle, have in many instances observed it.

Having thus taken a short view of the different characters employed by Conchologists in the arrangement of the testacea, and endeavoured to ascertain their relative importance, we shall conclude this part of the article by an application of the principles we have established, to an examination of the Linnaean genera, and to an enumeration of those genera which subsequent naturalists have formed, without, however, attempting to give a full list of such divisions, which have been multiplied beyond all bounds. We shall avoid a lengthened description of the species, as they are treated of very copiously in the body of the work. Our present object is to convey to the reader some farther remarks, illustrative of the history of the science.

LINNEAN GENERA.

1. CHITON. The only change which has taken

place in this genus, of any consequence, is its transference to the naked cephalous mollusca, effected by Lamark. The inhabitants bear a near resemblance to those of the genus Patella, and belong to the order Cyclobranchia of Cuvier. The marginal ligament which connects the testaceous plates, even after the extraction of the animal, is, in fact, the margin of its cloak, and offers more certain and convenient distinctions for the distribution of the species, than the number or appearance of the valves,—a character exclusively employed by Linnaeus. Eight species of this genus have been found on the British shores, which may be divided into the following sections:—1. Marginal ligament spinous, Ch. fascicularis. 2. Marginal ligament rough, Ch. marginatus, ruber, and cinereus. 3. Marginal ligament striated, Ch. laevis and albus. 4. Marginal ligament smooth, Ch. laevigatus. The Ch. crinitus, which Pennant obtained from the sea near Aberdeen, and Boys from Sandwich, is a species still involved in much obscurity, owing to the imperfection of the descriptions.

2. LEPAS. This genus has undergone several important alterations since the days of Linnaeus. As originally constructed by that author, it contained shells which differ widely from one another in habit and form. Bruguiere, the celebrated French Conchologist, separated the fixed shells furnished with an operculum, under the name of Balanus, and those which were seated on a peduncle, he retained under the generic name Anatifer. He thus suppressed entirely the Linnaean name of the genus. To the name of his first genus, we have no objections, but the second, though it records a curious fact in the history of popular errors, has been injudiciously selected. The name Lepas has been retained, by the best British writers, who have described seven species which live in our seas. These are distributed into two sections, according as the valves are five or more in number. The Lepas anatifer, is an example of the first division, and the L. scalpellum of the second.

The genus Balanus, as thus formed by Bruguiere, and represented by the Lepas balanus of Linnaeus, contained nineteen species. From these, Lamark has separated the B. diadema, testudinarius, and balanaris, to form his genus Coronula. These shells are conical, and have the compartments formed into twelve areas, six of these being depressed, and six elevated. They chiefly inhabit the skin of the whale, the base of the shell being placed in the fat. Lamark has likewise formed another genus, from two species analogous to the Coronulæ, which he terms Tubicinella, and characterizes it thus: "Testa univalvis, regularis, non spiralis, tubulosa, versus basin attenuata, utrinque truncata; apertura orbiculata terminali; operculo quadrialvi." The Lepas striata of Pennant ought also to form another genus, which might be termed Verrula, from the shell appearing like a wart on those bodies to which it adheres. It may be thus defined: "Shell with a thin testaceous base; sides depressed, composed of three obliquely ribbed rays. Mouth subquadrangular, closed by a two-valved lid."

Conchology. M. Dufresne (Annales du Museum, Vol. I. p. 465.) endeavours to prove by reasoning, that these shells are formed posterior to the birth of the animal. He supposes that, when they become too small to contain the inhabitants on account of their increasing size, the old shells are forsaken, and more commodious dwellings formed, until the animal reaches its full size. Other proof, however, than what the author adduces, is necessary to render the opinion probable.

Lamark, in his Système des Animaux sans vertèbres, placed these shells in a separate section at the end of the bivalves, and among the acéphalous mollusca. Afterwards he considered them as constituting a particular division of the crustaceous animals; and, lastly, he assigned them a place in his new class, which he terms CIRRHIPIDES. (See article CIRRHIPIDES.)

3. PHOLAS. This very natural genus was placed among the multivalves by Linnaeus, in the twelfth edition of his system. It is now united with the bivalves, the accessory plates at the hinge being regarded as of subordinate importance. In other respects, it has stood the test of modern innovation, with the exception of the genus GASTROCHENA of Spengler, in which the teeth are obsolete. This includes the Pholas hians of Chemnitz, and the Mya dubia of Pennant.

4. MYA. If we consider, as definite, the character assigned to this genus by Linnaeus himself, we shall find that it excludes many species which differ from the M. truncata, at present considered as the type of the genus. In this shell, the valves gape at both extremities, the ligament is internal, and placed on a thick erect tooth in one valve, not inserted into the opposite side. As the M. vulsella of Linnaeus is close at both ends, and destitute of a tooth, it has been separated from the true Mya, and formed into a distinct genus by Lamark, under the title VULSELLA. This shell presented some difficulty to Linnaeus, as he placed it at first among the Pinnæ and afterwards among the Myæ. Even Bruguiere gave it a place among the oysters.

Another genus has been formed by Lamark from the Mya siliqua of Chemn. (Conch. Vol. XI. p. 192, Tab. 198, fig. 1934.) He calls it GLYCIMERIS. Though nearly related to the true Myæ, by gaping at both extremities, yet it differs from them in the hinge, which is destitute of teeth, and in the ligament being external.

A new genus has been formed by M. M. Groye (Annales du Museum, Vol. IX.), which he terms PANOPRA, and assigns to it the following characters, "Coquille transverse, baillante inegalement au deux bouts, charnière semblable dans l'une et dans l'autre valve, ayant une callosité ou grosse dent allongée, placée en avant et sur le corselet; decurrente sur le bord intérieur, relevée en arête, mousse et saillante postérieurement; une dent cardinale conique un peu comprimée et arquée, et sur le valve droit une fossette dans laquelle s'engrène la dent de la valve opposée; ligament extérieur, crochets peu protubérans, corselet large, deux impressions musculaires dans chaque valve situées vers les extrémités." The type of this genus is the Myæ glycimeris of Gmelin first noticed by Aldro-

Conchology. vandus. It is inserted among the British shells by Mr Donovan upon very slight authority. In the construction of the genus, we think, that M. Groye has acted properly, but there was no necessity surely for changing the trivial name bestowed upon it by the discoverer. He has added another species from Monte Pulnasco in Parma. In the trivial name of this species, we consider that he has been guilty of an act of injustice. He has called it P. Faujas, in honour of Faujas St Fond, the zealous Professor of Geology in the Museum of Natural History at Paris. But the truth is, that it was found by M. Cortezi, Counsellor at Parma, and a successful investigator of the organic remains of that district. It ought, therefore, to have obtained the name of P. Cortezi, in honour of the discoverer, instead of the name of Faujas St Fond, who received it from M. Cortezi, and whose sole merit in the subject consisted in his bringing it in safety to Paris.

The principal error of Linnaeus in the construction of this genus, consisted in the insertion of fluviatile shells among his marine species. Bruguiere readily perceived this error, and formed a new genus for their reception, which he called UNIO. The M. Margaritifera, so famous for the production of pearls, the pictorum and ovalis belong to this genus, and are all found in rivers.

The late celebrated author of Testacea Britannica, separated a few species which had been considered as Myæ, such as the pubescens and pratensis, and formed for them a new genus, which he called LIGULA. Its character depends on the two broad spoon-shaped teeth at the hinge. With a little alteration, that genus might be prepared for receiving all the marine species, ejected from the genus Mya, on account of their being closed at the extremities.

There is one species among the British Myæ of Montagu, the inequivalvis which belongs to the genus CORBULA of Lamark. This genus was instituted to comprehend some fossil species found at Grignon, and is thus defined, "Testa bivalvis, inequilatera, subtransversa: natibus prominens incurvatis. Dens cardinalis unicus, conicus, recurvatus, teste oppositæ insertus. Ligamentum internum. Impressiones musculares duæ laterales." It contains but few recent species.

5. SOLEN. This genus has undergone few changes since the days of Linnaeus. The character has been somewhat restricted, and those species have been removed, in which the external margin is a little arcuated, and the cardinal teeth articulated, and two in number, and formed by Lamark into a new genus, which he terms SANGUINOLARIA. This includes the S. strigellatus of Linnaeus, the S. sanguinolentus of Gmelin, and we may add, as British species, the S. antiquatus and squamosus of Testacea Britannica. The animals of this genus, according to Poli, differ from the solens, in having the tubes of the syphon separate, and of unequal length and thickness. The S. minutus of Linnaeus, found in our seas, is referred to the genus HIATELLA by Cuvier, a genus very imperfectly defined, but nearly allied to the Byssomia of the same author, which includes the Mytilus rugosus of Linnaeus.

6. TELLINA. This extensive genus of Linnaeus

Conchology. the essential character of which is to have an anterior inflection or fold in each valve, and lateral teeth, includes many shells which differ greatly in form and habit, and which disagree even with his own definition. Hence several important improvements have taken place in the distribution of the species.

The first change in the genus of any consequence, consisted in the separation of the fluviatile from the marine species. This was accomplished by Scopoli (Introd. ad Hist. Nat. 397.), who bestowed on them the generic name of Sphærium. Bruguiere afterwards wantonly changed the name to CYCLAS, and this change has been embraced by Lamarck and other naturalists. We possess four British species of this genus, namely, cornea, lacustris, annica, and fluvialis. Montagu inconsiderately placed them among the cockles.

Another new genus of fluviatile shells, allied to the preceding, has been formed by Bruguiere and Lamarck for the reception of one species. The genus is termed GALATHEA, and the species G. radiata. There are two approaching hinge-teeth in the right valve, with a cavity in front, and two distant hinge-teeth in the left, with an intermediate large grooved callosity. The lateral teeth are of considerable size. The ligament is external, and the muscular impressions are two in number, and lateral.

The Tellina inequivalvis presents characters which readily distinguish it from the other species with which Linnæus placed it. The shell is inequivalve and inequilateral; the ligament is internal, and the lateral laminae are wanting. Besides, the animal differs from the other inhabitants of the Tellinæ, and is nearly related to the Solens. Hence Bruguiere formed a new genus for its reception, which he termed PANDORA.

There are several species of the genus Tellina and Venus, which Bruguiere and Lamarck have formed into a separate genus called LUCINA, which is thus characterized. "Testa bivalvis, æquivalvis, orbiculata, vel ovato transversa; natibus arcuatis, posticis versus. Cardo dentibus cardinalibus 1. s. 2. variabilibus; lateralibus 1. s. 2. remotis, interdum subnulis." To this genus Lamarck brings the Tellina lactea and divaricata of Linnæus, and the muricata of Chemn. (Conch. Vol. XI. p. 209. Tab. 199. fig. 1945-6.) together with the Venus fimbriata, and Pensylvanica of Linnæus, and the Jamaicensis of Chemn. (Conch. Vol. VII. p. 24. Tab. 39. fig. 408-9.) Cuvier, however, has restored the T. lactea to the genus Loripes, which Poli instituted for its reception.

7. CARDIUM. This is, perhaps, the best constructed genus which Linnæus formed. The characters are definite and obvious, and all the species are naturally allied. Hence no changes have taken place in their arrangement. The animal constitutes a new genus in the system of Poli, which he terms Cerastis.

Cuvier is disposed to constitute a new genus under the title HEMICARDIA, for the reception of the C. cardissa of Chemn., commonly called the Venus-heart cockle. The truncated appearance on the one side, and its being carinated in the middle, point out a conformation of the inhabitant different from the true cockles. Of this new genus we possess some fossil species.

8. MACTRA. The ligament, in the marine bi-valves, is, in general, placed on the outside, but in this genus, of which Lamarck has formed his family—Mactracea, the ligament is internal, and inserted in a cavity at the hinge formed for its reception. This family, as it stands at present, contains five well characterized genera.

In the restricted genus, MACTRA, as represented by the M. stultorum of Linnæus; the shell gapes a little, and the lateral teeth are strong, and lock into each other. The shells with age arrive at a considerable thickness. The inhabitant belongs to the genus Callista in the system of Poli.

The genus CRASSATELLA of Lamarck contains shells which close exactly, and whose lateral teeth are obsolete. He describes seven fossil species, and six recent ones, viz. Mactra glabrata, Encyclopédie Meth. Tab. 257. fig. 3.; Venus devancata of Martini, Conch. VI. p. 318. Tab. 30. fig. 317-18.; and the following new species, rostrata, Kingicola (from King's Island), donacina and sulcata, the three last discovered by Peron. The Mactra triangularis and minutissima of Testacea Britannica, probably belong to this genus.

The genus ERYCINA is composed entirely of fossil species. Lamarck has assigned it the following character: "Testa bivalvis, equivalvis, inequilatera, transversa. Dentes cardinales bini, superne divergentes, cum foveola minima intermedia: laterales compressi oblongi. Ligamentum foveola cardinali insertum." From the situation of the ligament being inserted in the small space between the teeth, the pit or cavity is less than in any of the other genera. The muscular impressions are two in number.

The transverse mactræ, which gape, but are destitute of lateral teeth, such as the M. lutraria of Linnæus, compose the genus LUTRARIA of Lamarck. The species already mentioned, the Mya oblonga of Gmelin, and the Mactra hians of Montagu, occur on our coasts; the former in great abundance at the mouths of the European rivers.

The genus UNGULINA, formed by Daudin, contains only one species, existing in the cabinet of Favanne. It is uncertain from what country it came. It is a regular longitudinal shell. The hinge is formed by one small tooth between two oblique pits. The muscular impressions are two in number. It is figured in Deterville's edition of Buffon. (Hist. Nat. des Coquil. Tom. XX. f. 2, 3.)

Another genus established by the same author, and termed Erodona, is subtransverse, irregular, and gaping, the hinge, in one valve, consisting of one hollowed tooth, and in the other a depression between two eminences. It includes two shells from the cabinet of Favanne. It is intermediate between the Mactræ and Myæ.

9. DONAX. The shells of this genus are readily known at first sight by their singular cuneiform shape. The hinge teeth are two in number, and the lateral teeth are spreading. The ligament is external, and, like the Tellinæ, it is placed on the shortest side. This is a circumstance of rare occurrence among the inequivalve testacea. The animal belongs to the genus Peronæa of Poli.

Lamarck has instituted a genus nearly allied to

Conchology. the preceding, termed PETRICOLA, the shells of which gape a little at both ends. There is one hinge tooth in one valve, and a bifid one in the other. The ligament is external; the muscular impressions are two in number; the structure of the hinge teeth, and the absence of the lateral teeth, at once distinguish this genus from the Donax and Venus. These animals are likewise peculiar in their habits. Lamarck quotes the Venus lithophaga of Retzius, Act. Acad. Tour. Vol. III. p. 11, and the Venus lapicida of Chemn. Conch. X. p. 356. Tab. 172, f. 1664-5. But Lamarck's genus has been again altered by Fleuriou-Bellevue, who has formed his genus RUPELLA, from the V. lithopagus of Retzius, and another species termed striata. Mem. del Acad. de la Rochelle, II. Tab. 2, fig. 9. In this genus the shell is transverse and inequilateral, compressed in the anterior part, and swollen behind. There are two crooked hinge teeth on each valve, one simple, the other bifid. The ligament is external, and there are two muscular impressions. The Donax irio belongs to this genus. The same author has formed two other genera of borers. The first he terms RUPICOLA, having a transverse inequilateral shell, a little gaping at the ends; no teeth, or callosities. In an internal projection of each valve, there is a pit for the ligament. The other genus is named SAXICAVA. It is transverse, inequilateral, and gaping, without teeth, or callosity, or pit. The ligament is external.

10. VENUS. This Linnæan genus contains so many species, that there is considerable difficulty in studying it. The formation of new genera, from its members, by diminishing their numbers, must prove highly acceptable to the student of Conchology. Lamarck has succeeded so far by previously restricting the character of the original as follows: "Testa bivalvis æquivalvis, subinæquila tera. Dentes cardinales 3 in utroque valva, ad nates basi convergentibus. Ligamentum externum, nymphas labiaque obtegens." The three diverging hinge teeth constitute the essential character of the genus, so that Lamarck has been able to form three other genera from different characters.

The genus CYTHREEA (the Meretrix of his Système des Animaux) is thus characterized: "Testa bivalvis, æquivalvis, subinæquilatera. Cardo dentibus duobus tribusve approximatis, basi convergentibus; uno solitario remotiuscula sub ano. Ligamentum ut in veneribus." It must be confessed that the insulated teeth under the lunule, in the absence of other characters, is obviously artificial. The following species are referred to this genus, Venus meretrix, punctata, læta, pectinata, tigerina, chione, erycina, &c.

The genus VENERICARDIA, formed for the reception of some fossil species, is thus defined: "Testa bivalvis, æquivalvis, inæquilatera, extus longitudinaliter costata. Dentes cardinales sub-bini crassi oblique secundi." The number of hinge teeth, and the longitudinal ribs, readily distinguish it from the genus Venus.

The other genus instituted by Lamarck, and termed by him CAPSA, has two teeth in one valve, and a bifid tooth in the other. The Venus deflorata of Linnæus is considered as the type of the genus.

Conchology. It was in the construction of the characters of the genus Venus that Linnæus indulged in obscene allusions. It is now time that the pages of natural history were freed from such pollution. Other names, more expressive, can easily be substituted, alike advantageous to the interests of science, and the reputation of the illustrious Swede.

11. SPONDYLUS. The shells which Linnæus included under this head are usually denominated prickly oysters. The genus is represented by the S. gæderopus of Linnæus. The S. plicatula of the same author has been separated from the Spondyli, and placed in a new genus, under the name PLICATULA. This genus differs from the former in the valves wanting ears, and in the absence of the triangular unsulcated space at the teeth of the under valve, so characteristic of the parent genus.

12. CHAMA. This is by no means a well constituted genus in the Linnæan system, as it includes shells possessing very different characters. It has, accordingly, undergone several important alterations. Bruguiere proceeded so far by establishing two new genera, and Lamarck, following the same plan, has added three more to the number. Those shells, which now belong to the genus CHAMA, are irregular, inequivalve, and adhere to other bodies. The hinge contains only one thick oblique tooth. It is represented by the Chama Lazarus of Linnæus.

The genus CARDITA, of Bruguiere, represented by the C. variegata, Lister, Tab. 344. fig. 84. consists of equivalve free shells, with the hinge furnished with two unequal teeth, the one situated under the beak, the other lateral, under the anterior margin.

The Chama cor of Linnæus appears to Lamarck possessed of sufficient characters to constitute a distinct genus, which he has named ISOCARDIA. It is an equivalve, free, regular, heart-shaped shell, with two cardinal teeth, and a separate lateral one, with separate, diverging, involuted beaks. It is an inhabitant of the British Seas.

To Bruguiere we owe the institution of the genus TRIDACNA, which is represented by the chama gigas of Linnæus, the largest shell in nature. The shell is equivalve and free. The hinge consists of two compressed teeth, and there is a gape at the lunule.

From the preceding genus of Bruguiere, Lamarck has separated the Chama hippopus of Linnæus, and formed from it a new genus, which he calls Hippopus. In its hinge it resembles the Tridacna, but differs in the structure of the lunule, which in this is closed.

The genus DICERAS of Lamarck, which he formed from the chama bicornis of Bruguiere, approaches the Isocardia in appearance, but the following character which he assigns, is fully sufficient for their discrimination: "Testa bivalvis inæquivalvis, adherens: natis conicis, maximis, divergentibus, in spiram irregularem contortis. Dens cardinalis maximus, crassus, concavus, auricularis in valvula majore. Impressiones duo musculares." It occurs only in a fossil state.

Before dismissing this Linnæan division of shells, we must notice another genus which has been added to it by Lamarck, from species brought from the Indian Seas. He terms it Etheria, and describes its generic character in the following words: "Coquille

Conchology: bivalve, inequivalve, irregulièr, adherente, a crochets court, enfoncées dans la base des valves et derigées de cote. Charnière sans dent; deux impressions musculaires séparées et laterales. Ligament demi-interieur, enveloppant une callosité oblongée, et sortant en de hors par une fisure recourbée." He has described four species which are very rugged on the outside, but finely naced within. Lamarck places this genus in his family Camacea, but in external aspect, and in the absence of teeth, they make a near approach to the Ostreaææ.

13. ARCA. Linnæus assimilated, under this genus, every shell the hinge of which presented numerous mutually inserted teeth. The shells which were thus united, have numerous relations, and constitute a very natural family. But in this family there are several groups of which Bruguiere formed sections and Lamarck genera. The genus ARCA is now restricted to those shells in which the hinge is in a straight line, and composed of numerous small lamelliform teeth, without lateral ribs. They have obtained their name from their resemblance to a ship, when the shell is inverted. Many species of this genus gape a little at the superior margin, to enable the animal to send out those tendinous threads by which it adheres to the rocks. The A. lactea, Noæ, and fusca, are natives of the British Seas.

The Linnæan Arcaæ, which have the hinge line broken and angular, belong to the genus NUCULA. In this genus, the beaks are contiguous, and turned a little backwards. The Nucula nucula, minuta, rostrata, and tenuis, are found on our shores.

In the genus PECTUNCULUS, the hinge teeth are situated on a curved line, the shell is nearly orbicular, and the muscular impressions, which are two in number, form each a callous projection with a sharp margin. The Arca pilosa and Glycymeris, both natives of Britain, are referable to this genus.

In the genus CUCULLÆA, the teeth of the hinge are similar to the Arcaæ, but at each extremity there are three or four transverse parallel ribs. It is represented by the Arca cucullata of Chemn. Conch. VII. p. 174. tab. 55. f. 526-528.

To the family Arcacea Lamarck has added another genus, which he terms TRIGONIA. The hinge teeth in this are only two in number, diverging and compressed, but they are transversely grooved on each side. The muscular impressions are two in number in the recent species, T. margaritacea, but in some of the fossil shells referred to in this genus, Mr Sowerby could observe only one. This may lead to the formation of a new genus.

14. OSTREA. Linnæus, in the construction of this genus, brought together many shells totally dissimilar in form, character, and habit, and hence it has undergone great alterations in the hands of succeeding Conchologists. To associate in one genus shells which remain immovably fixed to the rocks and stones from their birth, and which exhibit few other signs of vitality than the opening and shutting of their valves, with those which possess a locomotive power; to unite such as are irregular in their form and imbricated in their structure, with such as are of regular growth and solid texture, was surely to violate all the laws of a natural or an artificial system. Yet of

such incongruous materials is the Linnæan genus Conchology Ostrea composed, which, in spite of all its imperfections, has still its admirers in this country. (See Descriptive Catalogue, Lin. Trans.) The first important improvement in the reformation of the genus, consisted in the separation of the Pectens, which was executed by Pennant, and afterwards by Bruguiere and Lamarck. Since Lamarck has assigned new characters to the genus Ostrea, other separations must take place. It is thus defined: "Testa bivalvis inequivalvis, rudis adherens; cardine edentulo. Fossula cardinalis majoris valvæ ætate crescens. Ligamentum semi-internum. Impressio muscularis unica." He divides the genus into two sections; the first having the margin of the valves simple, as the common oyster; and in the second the margins are plaited, as in the O. crista-galli.

In consequence of this change in the generic character, the Ostrea malleus of Linnæus, Lister, Tab. 219, f. 54., has been formed by Lamarck into a new genus, which he calls MALLEUS. The shell is free, gapes a little at the beaks, produces a byssus, has no teeth in the hinge but a conical pit for the insertion of the ligament, placed obliquely on the margin of each valve. It was for a long time highly prized by collectors.

The genus PECTEN is one of the best characterized, most natural, and most beautiful, in the system. The shell is inequivalve and regular, the hinge is destitute of teeth, and the internal ligament is fixed to a triangular cardinal cavity. There are twelve species natives of our shores.

From the Ostrea perna, ephippium and isogonum, Bruguiere has formed the genus PERNA. The hinge is linear, and cut into a number of lengthened parallel veins, which receive the ligament. The interstices are formed into teeth, which simply oppose those of the other valve. In the anterior side of the valve, near the beaks, there is a callosity, and an opening for the byssus of the animal.

Lamarck has constituted another genus, nearly allied to the Perna, which he styles CRENATULA. The hinge in this genus presents only a row of pits for the ligament, which makes it appear crenulated. The intermediate spaces are not formed into teeth, neither is there any callosity, or opening for the byssus. He has figured two new species, which he terms avicularis and mytiloides, and a third is the Ostrea picta of Gmelin, Chemn. Conch. VII. p. 243. tab. 38. f. 575.

Nearly related to the Pecten is the genus LIMA of Bruguiere. The species differ, however, in the ligament being in a great measure on the outside. They are all of a white colour. The Ostrea lima is considered as the type of the genus.

The genus PECTUM of Bruguiere differs from the preceding in the ligament being external, and attached to a long straight fissure. The Ostrea spondiloidea of Chemn. Conch. VIII. t. 72. fig. 669, 670, is considered as the type of the genus.

To this family we must add two genera, possessed of very singular characters. They have neither hinge nor ligament. The first, instituted by the celebrated Botanist, Commerson, is termed ACARDO. The valves are depressed and nearly equal, and held

Conchology. together by the adductor muscle. The species at present known come from the eastern coast of Africa. The second is termed Radiolites, and was instituted by Lamarck. It differs from the former in the form of the valves, the inferior being turbinate, and the superior convex or conical. The species occur only in a fossil state, and have been long known to geognosts under the title Ostracites.

15. ANOMIA. In the Linnæan system, this genus is equally faulty as the last. It contains many species, which differ greatly from one another and from the generic character. Some are found recent on our shores, while others occur only in a fossil state. Lamarck, having rectified the Linnæan character of the genus, has separated many species, now grouped, into distinct genera. In the restricted genus ANOMIA, the under valve has a hole or groove near the beak, which is closed by a testaceous operculum. This appendage is fixed to rocks or stones, and has a ligament attached to it.

In the genus CRANIA, represented by the Anomia cranolaris of Linnæus, the under valve is pierced by three holes, which are oblique and unequal. It is much to be regretted that nothing is known concerning the animal.

Lamarck has instituted the genus GRYPHÆA from the Anomia gruphus of Linnæus. In this genus, the inferior valve is concave, terminating in a spirally involuted beak, projecting upwards; the upper valve is small, and resembles a lid. A transversely striated pit at the hinge contains the ligament. The only recent species known is called G. angulata. Many species are found in a fossil state in the rocks of this country.

Among the anomie, Linnæus placed the shells which compose the genus TEREBRATULA, whose characters are so obvious and distinct. In this genus, which is inequivalve and regular, the beak of the larger valve is produced, and pierced with a hole, through which the ligament of adhesion passes. There is one species, the T. cranium, a native of our seas.

From the Anomia placenta of Linnæus, Lamarck has formed his genus PLACUNA. The hinge is remarkable for two teeth on the one valve, placed like the letter V, the base toward the beak, and two impressions on the other valve. It occurs in the Indian Seas. The natives polish it for ornaments.

To Lamarck we are also indebted for having formed the genus CALCEOLA from the Anomia sandalum of Linnæus. The largest valve is sandal-shaped, and has at the hinge two or three small teeth. The other valve is small, flat, semi-orbicular, and resembles an operculum. It is frequent in a fossil state in Germany.

Mr Sowerby, in his valuable work on British Mineral Conchology, has made us acquainted with several new genera of fossil shells, which, by the older naturalists, would have been inserted in the genus Anomia. The genus PENTAMERUS is an equal-sided inequivalved bivalve, with one valve, divided by a longitudinal internal septum into two parts, the other by two septa into three parts or valve. Beaks incurved, imperforate. He has figured three species of this curious genus.

The genus PLAGIOSTOMA of Sowerby, is represented by the Pectenites Plagiostomus of Luid, Tab. 10, f. 639, and is thus defined: "An oblique cored bivalve, hinge destitute of teeth or internal pit. Line of the hinge straight in one valve, in the other deeply cut by an angular sinus." He gives figures of two species in his first volume, the Gigantea and the Spinosa. The former is the species of Luid.

The genus DIANCHORA is nearly related to the preceding, but in this the shell is fixed, and the attached valve has an opening in place of a beak. The other valve is beaked and cored. He describes two species, the D. lata and striata.

The Anomia spinosa of Linnæus probably belongs to Mr Sowerby's genus PRODUCTUS, which he thus defines: "An equilateral unequal-valved bivalve, with a reflexed, more or less cylindrical margin; hinge transverse, linear; beak imperforate; one valve convex, the other flat or concave externally." He gives figures and descriptions of seven species. It will be necessary to form many new genera for the reception of the fossil bivalve shells which are already known.

16. MYTILUS. Before proceeding to notice those new genera which have been formed from the Linnæan mytili, we may state, that the three parasitical species of the Systema Naturæ, belong to the genus OSTREA, to which they have been transferred by late authors. But improvements of a more important kind have been effected. Linnæus has associated together in this genus both fluviatile and marine shells. The former now constitute a very natural genus termed ANODONTA, of which the British rivers furnish three species, A. cygneus, anatinus, and avonenses. The muscular impressions are three in number.

It was easy to perceive that the Mytilus hirundo of Linnæus did not belong to the true mussels, since it is an inequivalve shell. Accordingly Lamarck has constituted a new genus for its reception, which he terms AVICULA. The Mytilus margaritiferus of Linnæus is of this genus. Mr Sowerby, in his Mineral Conchology, Vol. I. p. 14, informs us, that he has recent specimens of Avicula hirundo from Marazion and from Bantry Bay.

Lamarck, by restricting the characters of the genus Mytilus to include such species as have the beak terminal, has in this manner separated the transverse species to form the genus MODIOLA. The Mytilus modiolus of Linnæus is the type of the genus. It is common on the British shores, together with the Modiola discors and discrepans. We are at a loss to account for the scruples of Lamarck (Annales de Muscuss, Vol. X.) about considering this genus as byssiferous. Had he ever examined the figure of the type of the genus in Tab. 53 of Zoologia Danica, all his doubts would have been removed.

17. PINNA. No changes have taken place in this Linnæan genus, except that a few new species have been added. The Pinna pectinata ingens and muri-cata are found on our coasts.

In the course of our review of the Linnæan genera of bivalves, we have exposed some of those errors which the Swedish naturalist committed in associating discordant species under the same genus. Perhaps our examination of the univalves will make us

Conchology. better acquainted with the imperfections of that system, and dispose us to prize those improvements which subsequent naturalists have introduced.

18. ARGONAUTA. This genus, which contains but few species, is highly prized by collectors, who call the principal species by the name of Paper Nautilus. By restricting the characters of this genus, so as to embrace only those species in which the opening is interrupted by the involution of the spire, and in which the dorsal ridge is double, Lamark has been able to form the genus CARINARIA. In this the mouth is entire, and the dorsal ridge single. It is represented by the Argonauta vitrea of Gmelin.

19. NAUTILUS. Since the days of Linnæus, our knowledge of the Multilocular testacea has been greatly enlarged. He contented himself with arranging all the species with which he was acquainted under one genus, but, in consequence of modern industry, even the genera exceed the number of Linnæan species. Many recent species have been discovered by the aid of the microscope, among the sand on the sea shore, and a still greater number in a fossil state among the calcareous strata. These newly discovered kinds exhibit many different characters, and have compelled Conchologists to institute so many new genera for their reception, that the genus Nautilus of Linnæus appears rather as the head of a family or order, than as a separate genus of univalve shells. In this department the names of Bruguiere, Lamark, Montfort, Parkinson, and Sowerby, deserve respectful notice; and it is from their writings that the following remarks concerning the multilocular testacea have been extracted. The multilocular testacea may be divided into three sections: the first including those which are obviously spiral; the second, those which are produced; and the third, those which are of a globular or lenticular form. These sections are merely provisional, and are only intended to render more obvious and intelligible our notices of the genera.

1. The spiral multilocular testacea. At the head of this first division stands the modern genus NAUTILUS, in which the turns of the spire are contiguous, and the last whorl incloses the others. The partitions are perforated by a tube. We possess on our shores several species of this genus, of which the N. crispus is the most common.

In form, the genus LENTICULINA is nearly related to the former. The margin of the mouth reaches to the centre of the shell on both sides, and the partitions are destitute of a syphon. Lamark is in possession of a recent shell of this species from the sea near Teneriff.

The shells which Mr Sowerby, in his Mineral Conchology, has figured under the genus ELLIPSO-LITHES, have the whorls conspicuous, although the mouth clasps the body whorl. But it is easily distinguished from the other genera with which it is related by its elliptical form.

The genus DISCORBIS of Lamark (formerly called by him Planulites) bears a considerable resemblance to the nautilus in form, but the whorls are all apparent, and the partitions entire. The following species of the genus nautilus of Montagu, may be inserted in this genus, viz. crassulus, inflatus, carinatus

Beccarii and Beccarii perversus. Were we acquainted with the position of this last shell in the animal, we might, on account of its sinistral whorls, consider it as belonging to a new genus. The serpula lobata and concamerata of the same author, are nearly related to the present genus. But the circumstance of their being fixed shells, would induce us to form a new genus for their reception, which we term LOBATULA.

In the genus Rotalia, the spires approach to a conical shape, and the marginated trigonal aperture is reflected towards the base of the shell. It consists of shells which are now found in a fossil state.

The Nautilus spirula of Linnæus has afforded characters for the construction of a new genus termed SPIRULA. The whorls are separate, the mouth orbicular, the partitions perforated by a tube, and the last turn of the spire prolonged in a straight line. This last character was unknown to Linnæus, who had only seen the spiral body of the shell.

The genus SPIROLINA has the last turn of the spire produced like the preceding, but the whorls are contiguous. The partitions are perforated by a tube. The Nautilus semilituus and subarcuratulus of Montagu are of this genus.

The genus LITUOLA is allied to the spirula and spirolina in the production of the last whorl. The spires of the body are contiguous, and the partitions are pierced by a number of holes.

In the preceding genera the inner walls of the cavity are simple; but in the two following, the walls are formed into joints by sinuous sutures. The first of these is the AMMONITES, including those shells which have been termed cornua ammonis. The origin of this name is, by some, sought for in their resemblance to the horns of a ram; by others, to their having been found near the temple of Jupiter Ammon, in Upper Egypt. By the Indians, the Ammonites sacer is considered as a metamorphosis of the god Vishnu, and termed by them salgram or salgraman. It is found among the pebbles of the Gandica where it joins the Ganges. In this genus the whorls are contiguous, spiral, depressed, and obvious.

The ORBULITES of Lamark differs from the ammonites in the circumstance of the last whorl embracing and concealing the others. In both the syphon is marginal. The ammonites discus of Sowerby appears to be of this genus.

Nearly allied to the preceding is the TURRILITES of Montfort. It is similar in internal structure, but while the shells of the former are spirally discoid, those of the present genus are spirally turreted, resembling a Turbo or Turricula. Four species are figured by Sowerby in his Mineral Conchology, Vol. I.

The Genus SCAPHITES, formed by Parkinson, possesses very peculiar characters. It commences with a depressed volution, the last turn of which, after being enlarged and elongated, is diminished and reflected inwards.

2. Multilocular testacea with the shell produced. It must be confessed, that the genera of this section are but imperfectly understood. The recent kinds are too small to admit of any investigation of the animal, so that we are left entirely to conjecture.

Conchology. The genus HIPPURITES is of a conical form, and either straight or crooked. Within it is transversely chambered, and furnished with two lateral, longitudinal, obtuse, converging, ridges. The last chamber is closed by an operculum.

In the ORTHOCEA the shell is straight or slightly bent, and conical. The chambers are distinct, and pierced with a tube. We possess on our shores many minute species of this genus.

The genus BACULITES of Faujas St Fond, possesses a structure similar to the ammonites, the inner walls being articulated with sinuous sutures, and the partitions perforated. The shell is fusiform or bent into two parallel limbs. Mr Parkinson has contributed greatly to our knowledge of this genus, and has termed it Hamites. We prefer the name of the original discoverer to that of our English naturalist, which is very faulty. For, according to Pliny, "Hammites ovis piscium similis est."

In the BELEMNITES the shell is straight, conical, pointed, solid at the summit, and furnished with a lateral gutter. There is seldom more than one of the cells apparent, of a conical form, the older ones having been effaced in succession. The genus Tulaxodes of Guettard is not, perhaps, entitled to be considered as distinct.

The AMPLEXUS of Sowerby belongs to this division. It is nearly cylindrical, divided into chambers by numerous transverse septa, which embrace each other with their reflected margins. It contains one species from the limestone rocks of Ireland.

3. Multilocular testacea of a globular form. The first genus of this section is the MILIOLA. The shell is composed of three or four oval cells, turning round an axis parallel to their longest diameter. Many recent species of this genus are common on our shores: they were included by Montagu in his genus Vermiculum.

In the RENULINA the cells are narrow, linear, unilateral, curved into a part of a circle, and all situated on the same plane. The smallest cell forms a little arch round a marginal axis, and the others are placed contiguous to this on the same side. The species are all fossil.

The GYROGONA is a shell of a spheroidal form, composed of linear, curved, grooved, pieces, terminating in two poles. The external surface is obliquely spiral, the spires terminating at each pole. Found only in a fossil state.

The shells of the genus NUMMULITES are remarkable for their lenticular form. The external surface is smooth, and the cells concealed, but internally the transverse cells are disposed in a spiral discoid form. The cells are imperforate: they are the Camerine of Bruguière,—the Helecites of Guettard,—and the Discolithes of Fortis. This last author supposes, that they are formed in the interior of an animal analogous to the Sepia. The same opinion may, with propriety, be entertained of many other genera of multilocular testacea. Faujas St Fond found a recent specimen of a nummulite among the fragments of the Corallina officinalis, brought from the island of Corsica.

It is probable that the genus LAGENA, formed from the serpulae lagentæ of Walker's Testacea mi-

muta Rariora, belongs to the multilocular testacea; as in some of the species we have observed the appearances of internal divisions. Conchology.

As connected with this division of the Linnæan genera, we may take notice of the British shell called by Lightfoot Nautilus lacustris. (Phil. Trans. LXXVI. Tab. 1.) The very circumstance of its being a fresh water shell, distinguishes it sufficiently from all those which we have been considering, and its other characters are likewise peculiar. The partitions are distant, and consist of three testaceous plates, not united, which leave a sufficient opening between them to allow the animal to protrude and withdraw itself. It constitutes a distinct genus, which we have termed SEGMENTINA, from the trivial name bestowed on it by Solander, which refers to the structure of the septa. Its place in the system is next to the genus Planorbis.

These genera of multilocular shells which we have enumerated, are those which have been established with the greatest attention. Many other genera might have been enumerated, particularly those formed by Montfort, but the character given of them by Cuvier will satisfy the curiosity of the reader. When speaking of the Conchyliologie Systematique of that author, in reference to this subject, he says, "Où presque toutes les espèces et même des variétés sont erigées en genres."

19. CONUS. This genus is so very natural, that it has undergone no changes since the days of Linnæus, except the addition of new species. That author was acquainted with thirty-five species and a few varieties; but M. Hawss communicated to Bruguière descriptions of one hundred and forty-six, from specimens existing in his own cabinet. We cannot boast of any British species.

20. CYPREA. This genus is equally natural as the former. It has undergone no change since the days of Major. The C. Europæa and voluta are found on our coasts.

21. BULLA. This genus presents to the mere Conchologist a source of great perplexity. It displays at once the absurdity of dividing the molluscan animals into testaceous and naked, since no such distinction is observable in nature. Many of the shells which were formerly included in this genus are found to be contained within the common integuments of the animal. It was this circumstance which induced Linnæus to separate the Limax and the Aplysia from the vermes testacea. Both of these have shells, but they are concealed. In imitation of the same principle, Lamarck has formed a new genus among the naked mollusca, called BULLÆ, for the reception of those bullæ in which the shell is concealed. The Bulla aperta is the type of the genus. The Bulla plumula of Montagu is another shell included in the animal, which is very closely connected with the genus Pleurobranchia of Cuvier. (Annales du Mus. V. 269.) It may be asked, Are all the other Bullæ found in similar situations, and consequently do they belong to the naked mollusca? Lamarck considers, and apparently with reason, that all those which are distinctly spirally involuted, and ornamented with colours, are not entirely inclosed in the cloak of the animal, and ought therefore to

Conchology. be ranged with the testaceous mollusca. How few British species does this character include? As originally constituted, the genus of Linnaeus contained species of very different characters, so that many new genera have been formed. To Bruguiere, Lamarck, and Draparnaud, we owe all the improvements which have taken place.

The modern genus BULLA includes those shells which correspond with the following character: "Testa univalvis, convoluta, ovato-gibbosa vel cylindracea: spira non exserta, apertura longitudine testæ, labro acuto." The B. ampulla is the type of the genus.

The genus OVULA, instituted by Bruguiere, is more nearly related to the Cyprea than to the Bulla. It differs however from the former, in the left margin of the lip being smooth; and from the latter, in the edges of the mouth being rolled inwards, and in the shell being produced at both ends. The B. ovum of Linnaeus is the type of the genus; the B. patula of Pennant.

The Bulla terebellum has been employed by Lamarck to constitute his genus TEREBELLUM. The canal at the base of the mouth, and the truncated pillar, furnish the generic characters.

Linnaeus was, for some time, uncertain where to place those shells which he at last inserted in the genus Bulla, under the trivial names Ficus and Rapa. These, with a few of the murices of the same author, constitute the genus PYRULA of Lamarck. Its canaliculated base removes it from the Bullæ, while the short spire, the swelling of the last whorl, the smooth pillar, and pyriform shape, distinguish it from all those with which it is apt to be confounded. It is more nearly allied to the Fusus than to any other.

In the genus ACHATINA of Lamarck, the pillar is truncated as in the Terebellum, but the base of the mouth is entire. It is represented by the Bulla achatina of Linnaeus. To this genus we may refer the Buccinum acicula of Muller, which is found in England, and the Helix octona of Linnaeus, erroneously considered as a native of Britain.

The preceding genera consist of species which live in the sea. The B. virginea is a terrestrial shell, and ought to form a distinct genus next the Bulinus. The B. fontinalis, hypnorum, and rivalis, reside in fresh water. They have, with much propriety, been formed into a distinct genus by Draparnaud, which he calls PHYSA. They are all sinistral shells, and will require further division when the form of the animal shall become the basis of generic distinction. The fontinalis and hypnorum are natives of Britain.

22. VOLUTA. This genus, as originally formed by Linnaeus, depended, as he informs us, on the plicæ of the pillar, "volutæ genus facillime distinguitur columella plicata." But as this character belongs to many shells otherwise very different in form, succeeding Conchologists have separated many species from the genus, and reduced it within more natural limits. As it now stands, it is thus defined: "Testa univalvis, ovata, subventricosa, apice papillari; basi emarginata. Columella plicata; plicis inferioribus, majoribus, vel longioribus." The type of the genus is the Voluta musica.

Bruguiere removed from the Linnaean genus those

species which are destitute of a groove at the base of their mouth, and of which Lamarck formed the genera AURICULA, TORNATELLA, and VOLVARIA. In the latter the spire is not produced; in the former it is produced. To the genus Auricula, which contains land-shells, the V. auris-midæ and auris-judæ belong. The V. tornatilis is the type of the genus Tornatella. In his reference to the genus Volvaria, Lamarck quotes the Bulla cylindracea of Pennant and Da Costa, as if they were one and the same. But Pennant's shell is a true Bulla, while that of Da Costa is regarded as the Voluta pallida of Linnaeus, and probably belongs to this genus.

In the genus OLIVA, the turns of the spire are separated externally by a very distinct gutter or canal, and the pillar is obliquely striated. The Voluta oliva of Linnaeus contains many different species of this genus, which are remarkable for the smoothness of their surface, and the brilliancy of their colours.

The ANCILLA, which, like the former, is of a sub-cylindric form, is destitute of the groove which separates the whorls, and is characterized by an oblique callous ring at the base of the pillar.

In the genus MITRA of Lamarck, the spire is pointed instead of ending in a small knob, as in voluta, and the plicæ of the pillar increase in size from the base upwards, which is the reverse in that genus. The V. episcopalis of Linnaeus is the type of this genus, which contains many species much sought after by collectors.

In the COLUMBELLA, the shell is oval, the spire short, and the inner edge of the right lip is swollen. The V. mercatoria is the type of the genus.

The MARGINELLA is very distinctly marked by the prominent callous collar which surrounds the outside of the right edge of the shell. The opening of the mouth at the base is scarcely grooved. The V. glabella is the type of the genus.

The CANCELLARIA is nearly related to the genus columbella, but the absence of the swelling of the lip, and the presence of the compressed sharp plicæ of the pillar, furnish sufficiently obvious characters of distinction. The V. cancellata of Linnaeus is the type of the genus.

In the genus TURBINELLUS the shell is turbinated, subfusiform, and canaliculated at the base, having from three to five transverse compressed plicæ on the pillar. The V. pyrum is the type of the genus. Is not the V. hyalina of Montagu nearly allied to this genus?

23. BUCCINUM. This is another of the Linnaean genera of shells, which has undergone great alterations. As originally constructed, it embraced many distinct groups of shells, which Bruguiere and Lamarck have since formed into genera. The restricted character of the genus Buccinum is thus defined by the last mentioned author: "Testa univalvis, ovata vel elongata. Apertura oblonga, basi emarginata, nudata, canali nullo. Columella convexa plana."

Bruguiere separated the genus CASSIS, in which the opening is oblong and denticulated on the right side, with a short canal towards the back of the shell. The right margin has a callous border. The Buccinum cornutum of Linnaeus is the type of the species.

Conchology. The genus TEREBRA was likewise formed by the same author. It is remarkable for its turreted form, the spire being at least twice as long as the mouth, and the pillar at the base twisted. The B. maculatum of Lin. is the type.

In the genus NASSA the groove in which the mouth terminates is reflected as in Cassis, but the left edge of the mouth is callous, and forms upon the pillar a transverse fold. The B. arcularia of Lin. is the type.

The PURPURA is readily distinguished from the Buccinum and Murex, with which it has often been associated by its naked compressed pillar, ending in a point at the base. It includes our common littoral shell the Buccinum lapillus.

The genus DOLIUM is distinguished by its bellied forms and transverse rings, together with the margin on the right side being denticulated its whole length. The Buccinum galea of Linnæus is the type of this genus.

The genus HARPA is well known, and is distinguished by its sharp parallel longitudinal ribs. The pillar is smooth and pointed at the base.

In the genus EBURNEA, the shell is smooth, and the pillar umbilicated and subcanaliculated at the base. The Buccinum glabratum is the type of the genus.

24. STROMBUS. This Linnæan genus is now converted into a family, distinguished by the right margin changing its form with age, and having towards the base an indenture or sinus. It contains three genera, Strombus, Rostellaria, and Pterocera.

In the genus STROMBUS, the canal is short, the right margin is simple, and ends in a sinus. The S. pugilis of Linnæus is the type of this genus.

In the ROSTELLARIA the canal is produced into a long beak, the right edge of the mouth is entire, and rests above on the spire, and is sometimes decurrent. The sinus is contiguous to the canal. The R. cornuta of Mart. Conch. IV. Tab. 158. f. 1495, is the type of the species.

In the PTEROCERA the canal is also lengthened, but the right margin is dilated and digitated with a sinus near the base. The Strombus Pes-Pelicanii of our shores is of this genus.

25. MUREX. The modern genus of this name is thus defined by Lamark: "Testa univalvis, ovata, vel oblonga; basi caniculata; suturis varicoso-tumidis, sub asperis, longitudinalibus, et persistentibus." In consequence of this restriction, the five following genera have been instituted.

In the genus FASCIOLARIA, the spires are destitute of those longitudinal ribs which the Murex always exhibit, while the pillar is furnished with two or three oblique folds. The Murex tulipa of Linnæus is the type of this genus.

The shell of the genus FUSUS is lengthened, generally fusiform, destitute of longitudinal ribs, and bellied in the middle or lower part with a smooth pillar and lengthened canal. The F. longicauda, Lister, Tab. 918. f. 11. A. is the type.

The PLEUROTOMA is distinguished from the preceding by a sinus or groove, which appears on the margin of the right edge of the mouth, near its sum-

mit. It is represented by the M. Babylonius of Conchology. Linnæus.

The genus CLAVATULA differs from the former in possessing a short canal, and ought never to have been separated. We may refer to this the Murex sinuosa of Montagu, and M. emarginatus of Donovan.

In the genus CERITHIUM, the mouth is oblique, terminating below in a short truncated or recurved canal, and having at the upper part a gutter more or less produced. The Tympanotonos asper of Mart. Conch. 4. p. 314. Tab. 156. f. 1473, and 1474, is the type of the genus.

26. TROCHUS. This is a very natural genus in the Linnæan system, and has undergone few alterations in the hands of modern Conchologists. The T. perspectivis has given rise to a new and very obvious genus, termed SOLARIUM, characterized by the internal spiral edge of the umbilicus being crenulated. Another species, the T. labio, is the type of the genus MONODONTA, which contains shells of an oval form, with a rounded mouth, furnished with a tooth, formed by the truncated projecting base of the pillar: the two margins are separated. The turreted trochi of Linnæus constitute the genus PYRAMIDELLA.

The T. terrestris of British writers is so imperfectly described and figured, that it is impossible to assign it a place in the system. It is nearly allied to the helix.

27. TURBO. This very extensive genus has been greatly dismembered by modern Conchologists, in consequence of Lamark having restricted the character in the following terms: "Testa univalvis, conoidea vel subturrita. Apertura integra rotundata, edentula; marginibus superne semper disjunctis; columella basi planulata." Our T. littoreus is a good example of the restricted genus. In noticing the new genera which have been formed, we shall begin with the marine shells.

In the genus SCALARIA, the mouth is circular and bordered, with the margins united. The spires are covered with raised, edged, slightly oblique, longitudinal ribs. The famous wentletrap is the type of the genus.

Lamark thus defines his genus DELPHINULA: "Testa univalvis subdiscoidea vel abbreviato conica, solida, margaritacea, umbilicata; anfractibus subasperis. Apertura rotundata, marginibus orbiculatim connexis." The T. delphinus is the type of the genus. There are many species of turbines common on our shores, which are excluded by the preceding characters from the genera Turbo and Delphinula, such as the striatus, cingellus, Bryereus and others. They are distinctly turreted, with the margins of the mouth united, and may constitute a genus to be termed CINGULA.

The Turbo terebra of Linnæus serves as the type of another genus, termed TURITELLA, in which the margins of the mouth are disjoined, the spire regularly turreted, and the lip emarginated by a sinus. Nearly allied to the preceding is the genus PHASIANELLA, which Lamark thus defines: "Testa univalvis, ovata vel conica, solida. Apertura longitudi-

Conchology. nalis, ovata, integra; labro simplici acuto. Columella levis basi attenuata. Operculum calcareum vel corneum animali adherens."

Perhaps a rigorous examination of the turbines of British writers might justify the formation of one or two new genera; yet we shall content ourselves with noticing those species with which we have formed the genus OPOSTOMIA, in which the columella is furnished with a tooth. The Turbo interstincta, unidentata, plicata, Sandivicensis and insculpta of Montagu, are of this genus. They have no resemblance in their structure to the Linnæan volutæ; although they have been inconsiderately associated with them by the authors of the Descriptive Catalogue. The preceding genera are formed of marine shells; those that follow live on the land.

In the genus CYCLOSTOMA, the mouth is circular, with united and often reflected margins. The animal is furnished with an operculum. The T. elegans of Montagu is the only British species of the genus.

The species which are related to the T. bidens perversus and muscorum of Linnæus, constitute a very natural family, which may be termed PUPACEA, distinguished by the mouth being furnished with teeth or testaceous laminae, and the last whorl nearly the same or less than the preceding. Perhaps the most convenient way of dividing them is into two sections, the first including the dextral, and the second the sinistral shells.

The dextral pupacea form two genera. The PUPA, as originally constructed by Lamark, was equally faulty with many of the old Linnæan genera. As we have restricted it to include dextral shells, with the animal possessing four tentacula, with eyes at the tips of the two longest, we can receive into it the muscorum, sexdentatus, tridens, and juniperi of Montagu. In the genus CARYCHIUM, formed by Muller, the tentacula are only two in number, with the eyes placed at the base. It is represented by the T. carychium of Montagu.

The sinistral pupacea form likewise two genera. The first, which is the Clausilia of Draparnaud, contains sinistral shells, with the animal furnished with four tentacula, with eyes at the tips of the two longest. This contains the following British species,—perversa, nigricans laminata biplicata, and labiata. The other genus, called VERTIGO, was formed by Muller. The animal possesses only two tentacula, with the eyes on their tips. The T. vertigo is the type of the genus.

28. HELIX. Linnæus, in constructing this genus, attended only to the character of the mouth being contracted or lunated, without regarding the habits of the animals, or even the other forms which the shells exhibited. Hence he has united globose, discoid, and turreted, terrestrial, fluviatile, and aquatic shells; animals with two and with four tentacula, with and without an operculum, oviparous and viviparous.

The marine species of Linnæus are few in number. The genus JANTHINA of Lamark, has been formed from the H. janthina of Linn. a species which has lately occurred at several places of the Irish coast. The opening is triangular, and there is an angular sinus at the right edge. The shell, which

Linnæus terms H. halitoida, is completely conchology. cealed in the animal, and belongs to the genus Sigaretus, among the naked mollusca of Lamark. There are many marine shells inserted in the genus Helix by British writers, which either belong to the restricted genus Turbo, or to the Vermicularia.

The further reduction of the Linnæan helices depends on the separation of the terrestrial from the fluviatile shells, and subdividing these according to the characters furnished by the different groups.

Among the terrestrial shells, the restricted genus HELIX is by far the most extensive. It contains those shells which are subglobose, with a convex spire; the opening entire, wider than long, and diminished in its upper part by the projection of the last turn but one of the spire. The animal is furnished with four tentacula, with eyes at the tips of the two longest. The H. pomatia is the type of the genus.

The genus BULIMUS, as originally constructed by Bruguiere, was faulty in the extreme, but Lamark has new modelled it so as to include those land shells which are turreted or conical, with the mouth larger than broad, and having, in general, the margin reflected with age. Like the Helices, they have no operculum, and possess four subulated tentacula. The following are known as British species, B. obscurus, lubricus, Lackhamensis, and fasciata.

From the Helix succinea of Muller (the putris of Montagu and Donovan, not of Linnæus) Draparnaud has formed the genus SUCCINEA. The mouth is large in proportion to the size of the shell, and effuse at the base, with the outer lip thin, and the pillar attenuated. We are at a loss to account for the conduct of Lamark in substituting a new name for this genus without any apparent reason, and thus adding to the synonymes with which the science is already oppressed. The name first employed by Draparnaud, indicates one of the most striking characters of the type of the genus, whereas the term Amphibulina, used by Lamark, is founded on a mistake, and is apt to mislead. The H. succinea, although found in damp places, is not amphibious. It never enters the water voluntarily. Indeed, Muller says, "Sponte in aquam descendere nunquam vidi, a contra quoties eum aquæ immisi, confestim egrediebatur." The same remark is made by Montagu, and we have often witnessed its truth.

The Helix pellucida of Muller has been formed into a new genus by Daudebard, which he termed Helico-limax, but which Draparnaud, to avoid the use of a hybrid name, changed for the term VITRINA. Lamark has placed it among his naked mollusca, as the shell merely covers the superior parts, and the animal is furnished with a shield.

The fluviatile shells, included by Linnæus in his genus Helix, may, for the sake of present convenience, be considered as forming two sections, viz. those with and those without an operculum. To the former belongs the very natural genus LYMNEA, containing conical or turreted shells, with the right lip joined to the left at the base, and folding back on the pillar. The H. stagnalis of Linnæus, is the type of the genus, of which we possess ten British species. Two of these are truly amphibious, the octanfracta and fossaria.

Conchology. The genus PLANORBIS, instituted by Geoffroy or rather by Petiver, is remarkable for its discoid form, the spire revolving nearly in a horizontal line, so that all the whorls are obvious on both sides. Cuvier observed that the P. cornex was a sinistral shell, and it remains to be ascertained whether the whorls in the other species have a similar direction. We possess nine British species of this genus.

The operculated divisions of fluviatile helices, is more numerous than the preceding, containing at least six genera.

The genus VALVATA was instituted by Muller to include depressed shells with an orbicular mouth, the animal, furnished with three tentacula and a plumose appendage, considered as the branchiæ. The V. cristata (Helix crist. of Montagu), and piscinalis (the Turbo fontinalis of Montagu), are natives of this country.

The genus VIVIPARA, instituted by Geoffroy, and afterwards employed by Montfort, is represented by the H. vivipara of Linnaeus. It is the same as the Paludina of Lamarck. The shell is ovate or oblong, with a regularly elevated rounded spine. The aperture is entire, with the two lips united angularly at the summit. The type of the genus and the V. tentaculata, are natives of Britain.

In the genus AMPULLARIA of Lamarck, the shell is globose, the base umbilicated, and the mouth longer than broad. The H. ampullacea is the type of the genus.

In the genus HELICINA of Lamarck, the mouth is semilunar, the pillar callous and compressed below. The H. neritella, Lister, Conch. Tab. 61, fig. 59, is the representative of the genus.

In the genus MELANIA of Lamarck, the shells are turreted, longer than broad, effuse at the base, with a twisted solid pillar. The H. amarula is the type.

The genus MELANOPSIS was instituted by Daudebard to include the shells termed Melania by Olivier in his voyage to the Levant. The mouth is lanceolate, the pillar truncated and emarginated above, with a callosity at the base.

29. NERITA. This genus has been subdivided by Adanson and Bruguiere into NERITA and NATICA. In the former there is no umbilicus as in the N. eruvia, and, in the latter, there is an umbilicus, as in the N. canrena. Of the restricted genus nerita, we only possess one species, the littoralis, common on our shores. There are at least six species of Natica of British growth, the largest of which is the glaucina. The fresh water species have been formed by Lamarck, with great propriety, into a distinct genus, under the title Neritina. The N. fluviatilis occurs in the English rivers.

30. HALYOTIS. This genus has been dismembered of those species which are destitute of the perforations on the disk. These have been formed into a new genus, termed STOMATIA.

31. PATELLA. This genus, which at first sight appears so very natural, contains shells which exhibit considerable differences, both in form and structure, when narrowly examined. Geoffroy, with great propriety, separated the fluviatile species under the generic title ANCYLUS, a genus afterwards employed by Muller. The animal is essentially dis-

tinct from the marine patellæ. There are two species of this genus, the lacustris and fluviatilis, natives of Britain. Conchology.

The genus PATELLA, as circumscribed by Lamarck, is thus characterized: "Testa univalvis, non spiralis, clypeata vel subconica, imperforata, fissura marginali destituta cavitate simplici." The common Limpet may serve as the type of this genus.

In the genus FISSURELLA, established by Bruguiere, there is always an opening like a key-hole, near the summit of the shell. The F. græca and apertura are found on our coasts.

The genus EMARGINULA is readily distinguished by the slit or indentation which occurs on the posterior margin of the shell. Lamarck conjectures that the anus of the animal is situated at the hole at the summit of the fissurella, and at the posterior slit in this genus. In the genus CAPULUS of Montfort, the shell is conical, with the summit produced into a beak, more or less recurved, and twisted. The P. hungarica of Lister is the type. Cuvier seems inclined to place in this genus the Bulla velutina of Müller, the Helix levigata of British authors. The E. fissura is a native of our shores.

The genus CONCHOLEPAS is furnished with an operculum, and in form and habits approaches the Buccinum. It is represented by the P. integra of Da Costa's El. tab. 2, fig. 7.

In the genus CREPIDULA, the cavity of the shell is partially interrupted by a simple diaphragm. The P. porcellana is the representative of this genus. The C. chinensis inhabits the British seas.

In the preceding genus, the first approach to the turbinated shell makes its appearance, which becomes more obvious in the genus CALYPTREA, in which the cavity is furnished with a spiral diaphragm. The C. equestris is the type of the genus, which is related in part to the Trochi. From this genus of Lamarck, Montfort has separated the INFUNDIBULUM, as possessing a central spiral pillar. Sowerby has figured several species of this last genus in his Mineral Conchology as occurring in a fossil state in Britain.

The Patella unguis now ranks as a bivalve, and constitutes the genus LINGULA in the accephalous family Brachiopoda of Lamarck. Linnaeus, who never saw more than one valve, placed it among the Patella. Chemnitz, who examined both valves, considered it as a Pinna. These writers had overlooked the figure of the perfect shell, with its tube or stalk, as given by Seba, Vol. III. fig. 16. No. 4. This specimen, which belonged to Seba, passed into the museum of the Stadtholder, and afterwards reached, in company with the spoils of the other Continental collections, the Museum of Paris. Here Lamarck examined it, and formed his new genus. And the same specimen enabled Cuvier to investigate its anatomical structure, which he has explained in detail in the first volume of the Annales de Museum. Science has in this instance, as well as several others, profited by the successes of the Ex-Emperor of the French. This genus is destitute of a hinge. The valves are supported on a peduncle, and the shell is opened partly by the relaxation of the adductor muscle of the animal (and not by the external

Conchology. membrane, as stated by Mr Sowerby), and partly by the issuing forth of its spiral arms, which push asunder the valves like a wedge.

Cuvier has likewise constituted a new genus, which he terms ORBICULA, from the Patella anomala of Müller, Zool. Dan. Vol. I. p. 14. t. 5. The under valve is very thin, and fixed; the upper is orbicular, and depressed. It is a member of the same family as the preceding in the system of Lamark.

32. DENTALIUM. This very natural genus of Linnaeus has undergone no alterations. The Dentalium imperforatum, trachea, and glabrum of Montagu's Testacea Britannica, do not accord with the essential character of the Linnaean genus in being "utraque extremitate pervia." In consequence of this, we formed, some years ago, a new genus for their reception, called CÆCUM. They differ from the dentalia in being closed at the apex, and, in a natural arrangement, would probably be placed near the genus Vermicularia.

33. SERPULA. This genus has undergone several changes in the hands of modern Conchologists. The S. seminulum has been transferred to the genus Miliola, and the S. filogranum to the Tubipora. Besides these trivial alterations, the character has been greatly circumscribed, so as only to include shells which adhere to other bodies, and are tubular, entire, and flexuous, with a simple mouth, as represented by the S. contortuplicata of Linnaeus. The species which are regularly spiral, discoid, and fixed, as the S. spirorbis, now constitute the genus SPIRORBIS. But as there are both dextral and sinistral shells with this character, we propose to retain the dextral species in the genus Spirorbis, and form the genus HETERODISCA for the reception of the reversed species. Under each genus, we can rank six British species.

The genus VERMICULARIA is formed from those species which, in appearance, resemble the Spirorbis, but are not adherent, such as the S. lumbricalis. The shell at the mouth is, in general, somewhat produced. There are two or three minute British shells of this genus. As not very remotely connected with this genus, we may notice the EUOMPHALUS of Sowerby, which he styles "An involute compressed univalve; spire depressed on the upper part; beneath concave or largely umbilicate. Aperture mostly angular." It occurs in a fossil state.

The genus SILIQVARIA, represented by the S. anguina, is distinguished from the Serpula by a longitudinal, lateral, subarticulated fissure, which extends the whole length of the shell.

The genus PENICILLUS is formed from that curious shell the S. penis, and well known by the name of the watering-pot. The disk is perforated by a number of small holes.

34. TEREDO. From this genus, now considered as a bivalve (the tube being regarded as an accessory covering), the FISTULANA, of which the T. clava of Gmelin is the representative, has been separated. The external tube in this genus is closed at the posterior extremity, while in Teredo it is open. The S. polythalamia belongs, according to Lamark, to the Fistulana.

35. SABELLA. This last genus of the Linnaean vermes testacea has been degraded from its rank in

Conchology. The covering consists of agglutinated particles of sand and fragments of shells, and bears no resemblance to the testaceous coverings of the true mollusca. It is now placed in company with the Terebella among the annelides.

In the preceding review of the Linnaean genera of shells, the reader will probably have been astonished at those changes which have taken place. In this country we are so much accustomed to the artificial method both in Zoology and Botany, that we often reject, without sufficient consideration, the improvements which the study of the natural method has suggested. In the time of Linnaeus, perhaps, the genera of shells, with a few exceptions, were sufficiently numerous and commodious to embrace all the known species; but since the science has been cultivated with more zeal, in consequence, we must say, of the introduction of the natural method, the number of species has increased fourfold. New genera and orders, and other conventional divisions, have been formed, suited to the state of improvement of the science. The merit of all these improvements did not originate with Bruguiere or Lamark, whose names we have so often had occasion to mention. Many of the modern genera may be traced to the systems which prevailed before the days of Linnaeus,—systems which the Swedish Naturalist, in his desire to simplify, when simplicity was impracticable, too incautiously disregarded.

ON FOSSIL SHELLS.

Besides the shells which are found on the land, Fossil and in our lakes, rivers, and seas, and termed recent shells, there are relics of many species found in our marl-pits and limestone rocks, always somewhat altered in their texture, which are denominated fossil shells. While the shells of the former class have been eagerly sought after, few Conchologists have directed their attention to the condition or distribution of the fossil species. Nearly six hundred species of recent shells have been described as natives of Britain, while the fossil species, belonging to our strata, which have been accurately described, fall short of that number. There is, however, reason to believe, that the fossil species are more abundant.

It would have been a pleasant task for us to have entered into the details of this most important subject, but our limits permit us only to trace its outlines. Our remarks, however, we trust, will prove useful to those who are entering this fruitful field of investigation, and will embrace some observations on the systematic characters, condition, situation, and distribution, of these organic remains.

Systematic History of Fossil Shells. The determination of the characters of the fossil species of shells is attended with very great difficulty. The changes which they have undergone, and their union with the substance of the rock, prevent us from ascertaining, with any degree of accuracy, the peculiar marks by which the species are characterized. No trace of the animal remains, to aid us in the investigation, so that all our distinctions must rest on the characters furnished by the shell. This circumstance should prevent us from placing much confidence on the conclusions which have been drawn with respect to

Conchology. the resemblance between fossil species, and those which still exist in a living state.

The difficulty of determining the fossil species, and the reluctance to form new genera, rendered the descriptions of the older writers nearly unintelligible, although their figures are still useful to refer to. Lamarck, aware of the imperfection of the characters of the genera of recent shells, as connected with this subject, and possessing a rich cabinet of the fossil species found in the neighbourhood of Paris, devoted much time to the illustration of this subject, and with great success, as his various papers published in the Annales du Museum, abundantly testify. In this country, Parkinson, in his work entitled Organic Remains of a former World, has added some important illustrations of the genera of Lamarck, and has given some good descriptions of the species found in our rocks. Mr Sowerby, in his Mineral Conchology (publishing in numbers), is giving to the world excellent figures of the British fossil shells; but we regret to add, that he displays too great anxiety to constitute species; and the rocks, in which they are found imbedded, are but imperfectly characterised. But as the figures are well executed, they will prove highly useful to the British Mineralogist, by enabling him to refer to them with confidence, and to give names to those species which he meets with in the course of his investigations.

Chemical History of Fossil Shells. When we consider the elements of which shells are composed, and the nature of their combination, we might be ready to expect that fossil shells would differ but little in structure from recent species. But the case is widely different. In many instances, the confused foliaceous structure which prevailed in the recent shell, has given place to a new arrangement of the particles, and the fossil shell exhibits a foliated crystalline structure. Here solution and precipitation have taken place in the same spot. In some cases the calcareous matter of the shell has become impregnated with foreign ingredients, or has totally disappeared, leaving in its place ferruginous or siliceous deposits. But the most curious circumstance in the chemical history of these fossils, is the preservation of the animal matter of the shell into its original form and order of arrangement, even when the calcareous matter of the shell has been changed into compact or granular limestone. This very important fact we owe to the ingenuity of Mr Parkinson, who, by treating the shell for a length of time with greatly diluted acid, abstracted the calcareous matter, and obtained a distinct view of the cartilaginous membranes of the shell. The student will in general observe, that the cavities of those shells, which present an external opening, are filled with the same sort of matter as the rock in which they are enclosed; while the cavities of the multilocular testacea, which have no external communication, are filled with matter invariably of a crystalline structure, even when not different from the substance of the rock.

Geognostic History of Fossil Shells. It appears evident that the advancement of this branch of Conchology must, in a great measure, depend on the accurate discrimination of the fossil species, and the relations of the rocks in which they are contained.

It is only within the last twenty years, therefore, that our knowledge of this branch of the subject has been acquired. Werner has contributed largely to our stock of knowledge, but much yet remains to be brought to light. The following notices may be regarded as embracing the principal facts which have been ascertained.

In those ancient strata upon which all the others are incumbent, and which are called Primitive, no remains of shells, or other relics of organized bodies, have hitherto been detected. These rocks are therefore supposed to have received their arrangement previous to the creation of animals or vegetables. In that group of rocks which rests upon the primitive strata, and to which Mineralogists give the name of Transition, fossil shells, as well as the remains of vegetables, have been observed. The shells exhibit such striking peculiarities of form, and bear so remote a resemblance to the recent kinds, that they are considered as the remains of species which do not now exist in a living state on the globe. They are much changed in their texture, and in general intimately united with the contents of the stratum. They are chiefly found in the beds of limestone, sometimes also in the greywacke and clay state. In the numerous and ill-characterized series of strata which are incumbent on the transition class, and to which Mineralogists attach the term Floetz, the remains of shells are much more numerous. In the older members of this class, such as the red sandstone and independent coal formations, the shells, though generally different in form from those of the preceding class, are still dissimilar to the recent species, and no longer exist in a living state. In the newer members of this class, however, such as the gypsum and chalk rocks, the species bear a much closer resemblance to the existing races, and several species cannot be distinguished from them by any satisfactory characters furnished by the shell. The fossil species found in the rocks of the older members of the class are greatly altered in their texture, and, in many cases, intimately united with the substance of the beds; the shells belonging to the newer members, are much less altered in their form and texture, separate more readily from the surrounding rocks, and appear like recent shells somewhat weathered. The shells are found in nearly all the different kinds of rock, but are more numerous in the calcareous strata. In the alluvial strata, fossil shells are frequently to be met with. The species which here present themselves bear so close a resemblance to the existing kinds, that Conchologists are disposed to consider them as the relics of animals which still exist. In many cases, the prototypes may be found on the neighbouring shore or lake, but in other instances they must be sought for at a greater distance. These shells are found in beds of gravel and sand, and likewise in great abundance in shell marl.

It appears, then, that the shells in the older strata differ specifically from those which the newer strata contain; and that they have belonged to molluscous animals, which no longer exist in a living state on this globe; that, in the newer strata, the fossil shells bear a closer resemblance to existing species; and that in the last formed strata, remains of species actually existing are to be met with.

In this distribution of the remains of testaceous animals we likewise perceive that, in the older strata, the inequalvalved and multilocular shells are more numerous than the other kinds; and that the canalculated univalves are seldom to be met with in the transition or older members of the Floetz series, but that they become more numerous in the newer members of the Floetz rocks, and in the alluvial strata. Circumstances of this kind induced Werner to conclude that different formations could be discriminated by the petrifications which they contain. From the difficulty of distinguishing the fossil species, however, joined with our ignorance of their geographical distribution, few Mineralogists have suffered their conclusions to be much influenced by this rule.

It will likewise be observed, that the shells in the newer strata are but little changed, while those in the older rocks are greatly altered in their texture, and in part obliterated. The same power which rendered the rock compact or crystalline, has likewise exerted its influence on the imbedded remains. In the newest strata, this power has scarcely begun to operate; so that the imbedded shells still retain in perfection their original characters.

In examining a limestone quarry, for example, the student will perhaps be surprised to find petrifications of shells in the bed of limestone, while, in the sandstone covering, he witnesses impressions of plants unaccompanied with shells. In order to gain more correct ideas on this subject, let him repair to a marl bog, and he will there find the bed of marl abounding in shells, while in the bed of sand below, on which it rests, or of peat moss, which covers it, he will find exclusively the remains of vegetables. Here let him study the subject, while the strata are yet recent, and while lapidification is only commencing. There is, however, this difference between the shells in the marl and those in the limestone, that individuals of the former species still exist, while no living examples of the latter are known.

Geographical History of Fossil Shells. As the geographical distribution of recent shells is a branch of Conchology to which few have devoted their attention, and about which very little is known, we can scarcely expect to find the geographical distribution of the fossil species more fully illustrated. We know, with regard to the recent shells, that some species which are found in the bays of Norway and Greenland occur also on the shores of the Mediterranean, and that the British Isles have several species in common with Africa and the West Indies. Still we know not, with any degree of accuracy, the geographical range of any one species. Geologists ought, therefore, to exercise a great degree of caution in drawing conclusions concerning the original situation of those shells which they find in a fossil state. When a fossil shell is discovered in the strata of this country, which bears a close resemblance to the recent shells of distant seas; many inquirers, without waiting until they have established the identity of the species, and without any precise information with regard to the geographical distribution of that species, conclude that this fossil shell must have been brought from these distant seas, and conveyed to its present situation by some mighty torrent. Instances of this mode of reasoning could easily be

pointed out in the writings of British and Continental Conchology. Mineralogists.

In every country there are particular animals and vegetables, which indicate, by their mode of growth and rapid increase, a peculiar adaptation to the soil and climate of that district. Hence we find a remarkable difference in the animals and plants of different countries. Many shell-fish have indeed a very wide range of latitude, through which they may be observed; but we know, that the same molluscous animals which are natives of Britain, are not found, as a whole, as natives of Spain, while the molluscous animals of Africa differ from both. If the same arrangement of the molluscous animals always prevailed in the different stages of their existence, then we may expect to find the fossil shells of one country differing as much from those of another, as the recent kinds are known to do, so that every country will have its fossil, as well as its recent testacea. Few observations illustrative of this branch of the subject have hitherto been published.

It has often been remarked, that the fossil shells (and the relics of other animals and plants) found in the strata of this country, are very different in their appearance from those shells of the mollusca which at present exist in the country, but that they bear a close resemblance to the existing species of the equatorial regions. This very important observation would lead us to conclude, that the mollusca which lived in this country at the period of the formation of the strata in which they are now enclosed, were influenced by different physical circumstances, from those, by which the forms of the recent kinds are regulated; but it by no means warrants the conclusion, that those shells once lived in the equatorial regions, and that a mighty deluge transported them to their present situation. This last conclusion can never be admitted by those who have witnessed the perfect preservation of the different parts of fossil shells, their valves, spires, protuberances, and delicate spines, still unbroken. Though these species no longer exist, in a living state, in this country (nor on the globe), we must admit the conclusion of Werner (with regard to fossil plants), that they lived and died in the country where their relics are now found.

It would form a very curious subject of inquiry to ascertain the character of those fossil shells which are found in the strata near the equator. If they likewise differ from the recent species of those seas, and if, in appearance, they resemble the productions of arctic regions, we might then speculate, with more success, upon those mighty revolutions which have taken place on the earth's surface, and trace in the mineral kingdom the proofs of those changes which animals and vegetables have experienced. In the meantime, we would recommend the examination of the laws which regulate the physical and geographical distribution of recent shells, as the most suitable preparation for investigating the condition of those extinct races, whose memorials are preserved in strata, differing from one another in structure, position, and composition.

See MOLLUSCA for a classification of shells whose animals are known, and SHELLS for a description of the genera whose animals are unknown.