SHELL

SHELL, in natural history, a hard, and, as it were, stony covering, with which certain animals are defended, and thence called shell-fish.

The singular regularity, beauty, and delicacy in the formation of the shells of animals, and the variety and brilliancy in the colouring of many of them, at the same time that they strike the attention of the most inquisitive observers, have at all times excited philosophers to inquire into and detect, if possible, the causes and manner of their formation. But the attempts of naturalists, ancient and modern, to discover this process, have constantly proved unsuccessful. M. de Reaumur hitherto appears alone to have given a plausible account, at least, of the formation of the shell of the garden-snail in particular, founded on a course of very ingenious experiments, related in the Paris Memoirs. He there endeavours to show, that this substance is produced merely by the perspirable matter of the animal condensing, and afterwards hardening on its surface, and accordingly taking the figure of its body, which has performed the office of a mould to it; in short, that the shell is of a snail, and, as he supposed, of all other animals pos-

sessed

fessed of shells, was only the product of a viscous transudation from the body of the animal, containing earthy particles united by mere juxtaposition. This hypothesis, however, is liable to very great and insurmountable difficulties, if we apply it to the formation of some of the most common shells: for how, according to this system, it may be asked, can the oyster, for instance, considered simply as a mould, form to itself a covering so much exceeding its own body in dimensions?

M. Herissant, in the Memoirs of the Academy of Sciences for 1766, has discovered the structure of shells to be organic. In the numerous experiments that he made on an immense number, and a very great variety, of animal shells, he constantly found that they were composed of two distinct substances; one of which is a cretaceous or earthy matter; and the other appeared, from many experiments made upon it by burning, distillation, and otherwise, to be evidently of an animal nature. These two substances he dexterously separated from each other by a very easy chemical analysis; by the gentle operation of which they were exhibited distinctly to view, without any material alteration from the action of the solvent, or instrument employed for that purpose. On an entire shell or a fragment of one, contained in a glass vessel, he poured a sufficient quantity of the nitrous acid, considerably diluted either with water or spirit of wine. After the liquor has dissolved all the earthy part of the shell (which may be collected after precipitation by a fixed or volatile alkali), there remains floating in it a soft substance, consisting of innumerable membranes of a retiform appearance, and disposed, in different shells, in a variety of positions, which constitutes the animal part of it. This, as it has not been affected by the solvent, retains the exact figure of the shell; and, on being viewed through a microscope, exhibits satisfactory proofs of a vascular and organic structure. He shows that this membranous substance is an appendix to the body of the animal, or a continuation of the tendinous fibres that compose the ligaments by which it is fixed to its shell; and that this last owes its hardness to the earthy particles conveyed through the vessels of the animal, which fix themselves into, and incrust, as it were, the meshes formed by the reticular filaments of which this membranous substance is composed. In the shell called porcelaine, in particular, the delicacy of these membranes was so great, that he was obliged to put it into spirit of wine, to which he had the patience to add a single drop of spirit of nitre day by day, for the space of two months; lest the air generated, or let loose by the action of the acid on the earthy substance, should tear the compages of its fine membranous structure into shatters; as it certainly would have done in a more hasty and less gentle dissolution. The delicate reticulated film, left after this operation, had all the tenacity of a spider's web; and accordingly he does not attempt to delineate its organization. In other shells he employed even five or six months in demonstrating the complicated membranous structure of this animal-substance by this kind of chemical anatomy. In general, however, the process does not require much time.

Their membranous structure produces great variety of colours.

Of the many singular configurations and appearances of the membranous part of different shells, which are described in this memoir, and are delineated in several well executed plates, we shall mention only, as a spe-

cimen, the curious membranous structure observed in the laminae of mother-of-pearl, and other shells of the same kind, after having been exposed to the operation of the author's solvent. Beside the great variety of fixed or permanent colours with which he found the animal-filaments of these shells to be adorned, it is known, that the shell itself presents to the view a succession of rich and changeable colours, the production of which he easily explains from the configurations of their membranes. Nature, he observes, always magnificent in her designs, but singularly frugal in the execution of them, produces these brilliant decorations at a very small expence. The membranous substance above-mentioned is plaited and ruffled, as it were, in such a manner, that its exterior laminae, incrust with their earthy and semi-transparent matter, form an infinite number of little prisms, placed in all kinds of directions, which refract the rays of light, and produce all the changes of colour observable in these shells.

With respect to the figures and colours of shells, it is observed, that river shells have not so agreeable or diversified a colour as the land and sea shells; but the variety in the figure, colours, and other characters of sea shells, is almost infinite. The number of distinct species we find in the cabinets of the curious is very great; and doubtless the deep bottoms of the sea, and the shores yet unexplored contain multitudes still unknown to us. Even the same species differ in some degree in almost every individual; so that it is rare to find any two shells which are alike in all respects.

This wonderful variety, however, is not all the produce of one sea or one country; the different parts of the world afford us their different beauties. Honan beautiful shells are obtained with some from the East Indies and from the Red sea. This is in some degree countenanced by what is found to this day; and from the general observations of the curious, it seems, that the sun, by the great heat that it gives to the countries near the line, exalts the colours of the shells produced there, and gives them a lustre and brilliancy that those of colder climates always want; and it may be, that the waters of those vast seas, which are not subject to be weakened by fresh rivers, give a nourishment to the fish, that may add to the brilliancy of their shells.

The shores of Asia furnish us with the pearl-oysters shells and scallops in great perfection. About Amboyna are found in the most beautiful specimens of the cabbage-shell, Ab. the arrosier, the ducal mantle, and the coral oysters, or echinated oysters. Here also are found a great variety of extremely beautiful murexes, telline, and volutes; some fine buccinum, and the shell called the Ethiopian crown, in its greatest perfection. The dolia, the murexes, and the cassandres, are also found on these coasts in great beauty. Many elegant snails and screw-shells are also brought from thence; and finally, the serapion and spider-shells. The Maldive and Philippine islands, Bengal, and the coast of Malabar, abound with the most elegant of all the species of snails, and furnish many other kinds of shells in great abundance and perfection. China abounds in the finest species of porcelain shells, and has also a great variety of beautiful snails. Japan furnishes us with all the thicker and larger bivalves; and the Isle of Cyprus is famous above all other parts of the world for the beauty and variety of the patella or limpet found there.

America affords many very elegant shells, but neither in so great abundance nor beauty as the shores of Asia. Panama is famous for the cylinders or rhombi, and we have beside, from the same place, some good porcelains, and a very fine species of dolium, or concha globosa, called from this place the Panama purple shell. One of the most beautiful of the cylinders is also known among our naturalists under the name of the Panama shell. About Brasil, and in the gulf of Mexico, there are found murices and dolia of extreme beauty; and also a great variety of porcelains, purpure, pectens, neritæ, buccardia or heart-shells, and elegant limpets. The isle of Cayenne affords one of the most beautiful of the buccinum kind, and the Midas ear is found principally about this place. Jamaica and the island of Barbadoes have their shores covered with porcelains, chamæ, and buccina; and at St Domingo there are found almost all the same species of shells that we have from the East Indies; only they are less beautiful, and the colours more pale and dead. The pearl-oyster is found also on this coast, but smaller than in the Persian gulf. At Martinico there are found in general the same shells as at St Domingo, but yet less beautiful. About Canada are found the violet chamæ, and the lakes of that country abound with muscles of a very elegant pale blue and pale red colours. Some species of these are remarkably light and thin; others are very thick and heavy. The Great Bank of Newfoundland is very barren in shells: the principal kind found there are muscles of several species, some of which are of considerable beauty. About Carthagenæ there are many mother-of-pearl shells, but they are not of so brilliant colours as those of the Persian gulf. The island of Magellan, at the southern point of America, furnishes us with a very remarkable species of muscle called by its name; and several very elegant species of limpets are found there, particularly the pyramidal.

In Africa, on the coast of Guinea, there is a prodigious quantity of that small species of porcelain which is used there as money; and there is another species of porcelain on the same coast which is all over white: the women make bracelets of these, and the people of the Levant adorn their hair with them. The coast of Zanguebar is very rich in shells: we find there a vast variety of the large porcelains, many of them of great beauty; and the nax maris or sea-nut is very frequent there. Beside these, and many other shells, there are found on this coast all the species of nautili, many of which are very beautiful. The Canary isles abound with a vast variety of the murices, and some other good shells; and we have from Madeira great variety of the echini or sea-eggs different from those of the European seas. Several species of muscles are also common there, and the auris marina is nowhere more abundant. The Red sea is beyond all other parts of the world abundant in shells, scarce any kind is wanting there; but what we principally have from thence are the purpure, porcelains, and echini marini.

The Mediterranean and Northern ocean contain a great variety of shells, and many of very remarkable elegance and beauty; they are upon the whole, however, greatly inferior to those of the East Indies. The Mediterranean abounds much more in shells than the Ocean. The gulf of Tarentum affords great variety of purpure, of porcelains, nautili, and elegant oysters; the coasts of Naples and Sardinia afford also the same, and

with them a vast number of the solens of all the known species. The island of Sicily is famous for a very elegant kind of oyster which is white all over; pinnae marinae and porcelains are also found in great plenty there, with tellinæ and chamæ of many species, and a great variety of other beautiful shells. Corsica is famous, beyond all other places, for vast quantities of the pinnae marinae; and many other very beautiful shells are found there. (Lilley, Hist. Conchyl.) About Syracuse are found the gondola shell, the alated murex, and a great variety of elegant snails, with some of the dolia and nerite. The Adriatic sea, or gulf of Venice, is less furnished with shells than almost any of the seas thereabout. Muscles and oysters of several species are however found there, and some of the cordiform or heart-shells; there are also some tellinæ. About Ancona there are found vast numbers of the pholades buried in stone; and the auræ marinae are particularly frequent about Pizzoli. (Bonani, Recreat. Ment. et Ocul.)

The ports of Marfeilles, Toulon, and Antibes, are full of pinnae marinae, muscles, tellinæ, and chamæ. The coasts of Bretagne afford great numbers of the conchæ anatiferæ and poussipieds; they are found on old rotten boards, on sea substances, and among clusters of sponges. The other ports of France, as Rochelle, Dunkirk, Brest, St Maloe, and others, furnish oysters excellent for the table, but of the common kind, and of no beauty in their shells; great numbers of muscles are also found there; and the common tellinæ, the onion-peel oysters, the solens, and conchæ anatiferæ, are also frequent there. At Granville, in Lower Normandy, there are found very beautiful pectens, and some of the cordiform or heart-shells.

Our own English coasts are not the least fruitful in shells, tho' they do not produce such elegantly painted ones as the Indies. About Plymouth are found oysters, muscles, and solens, in great abundance; and there, and on most of our other shores, are numbers of the auræ marinae and dentalia, with pectens, which are excellent food; and many elegant species of the chamæ and tellinæ are fished up in the sea about Scarborough and other places. Ireland affords us great numbers of muscles, and some very elegant scallop-shells in great abundance, and the pholades are frequent on most of our shores. We have also great variety of the buccina and cochlear, some volutæ; and, on the Guernsey coast, a peculiarly beautiful snail, called thence the Guernsey snail.

The coasts of Spain and Portugal afford much the same species of shells with the East Indies, but they are of much fainter colours, and greatly inferior in beauty. There are, according to Tavernier and others, some rivers in Bavaria in which there are found pearls of a fine water. About Cadiz there are found very large pinnae marinae, and some fine buccina. The isles of Majorca and Minorca afford a great variety of extremely elegant shells. The pinnae marinae are also very numerous there, and their silk is wrought into gloves, stockings, and other things. The Baltic affords a great many beautiful species, but particularly an orange-coloured pecten, or scallop-shell, which is not found in any other part of the world.

The fresh water shells are found much more frequently, and in much greater plenty than the sea-shells. There is scarce a pond, a ditch, or a river of fresh water in any part of the world in which there are

are not found vast numbers of these shells with the fish living in them. All these shells are small, and they are of very little beauty, being usually of a plain greyish or brownish colour. Our ditches afford us chame, buccina, nerite, and some patellæ; but the Nile, and some other rivers, furnished the ancients with a species of tellina which was large and eatable, and so much superior to the common sea tellina in flavour, that it is commonly known by the name of tellina regia, "the royal tellina." We have a small species of buccinum common in our fresh waters, which is very elegant, and always has its operculum in the manner of the larger buccina; a small kind of muscle is also very common, which is so extremely thin and tender, that it can hardly be handled without breaking to pieces. The large fresh water muscle, commonly called in England the horse-muscle, is too well known to need a description; and the size sufficiently distinguishes it from all other fresh water shells.

In collecting shells, it is most advisable, whenever it can be done, to get those which have in them the living animals; because we shall thus obtain the natural history of the animals, and the shells themselves in their natural beauty, and the full glow of their colours. Shells should be also procured from the deeper parts of their resorts, and immediately after storms on the sea beaches and shores; because, by being much exposed to the sun, their colours fade, and they are liable to other accidents that injure them. In order to kill the fish that inhabits them, Mr Da Costa advises to give them a quick dip in boiling water, and when they are cooled, to lay them in cold water till they are cleaned; and in this operation they should not be touched with aquafortis, or any other acid, nor exposed to the heat of the fire and sun.

The art of polishing shells arrived but lately at its present state of perfection; and as the love of sea shells is become so common among us, it may not be disagreeable to the reader to find some instructions in executing so pleasing a method of adding to their natural beauty, the rules for which are at present so little known, though the effect of them be so much esteemed.

Among the immense variety of shells which we are acquainted with, some are taken up out of the sea, or found on its shores in all their perfection and beauty; their colours being all spread by nature upon the surface, and their natural polish superior to any thing that art could give. Where nature is in herself thus perfect, it were madness to attempt to add any thing to her charms: but in others, where the beauties are latent and covered with a coarser outer skin, art is to be called in; and the outer veil being taken off, all the internal beauties appear.

Among the shells which are found naturally polished are the porcelains, or cowries; the cassanders; the dollia, or conchæ globosæ, or tuns; some buccina, the volutes, and the cylinders, or olives, or, as they are generally though improperly called, the rhombi; excepting only two or three, as the tiara, the plumb, and the butter-tub rhombus, where there is an unpromising film on the surface, hiding a very great share of beauty within. Though the generality of the shells of these genera are taken out of the sea in all their beauty, and in their utmost natural polish, there are several other genera, in which all or most of the species are taken up naturally rough and foul, and covered with an epidermis, or coarse

outer skin, which is in many rough and downy or hairy. The tellinæ, the muscles, the cochleæ, and many others, are of this kind. The more nice collectors, as naturalists, insist upon having all their shells in their native and genuine appearance, as they are found when living at sea; but the ladies, who make collections, hate the disagreeable out-sides, and will have all such polished. It would be very advisable, however, for both kinds of collectors to have the same shells in different specimens both rough and polished: the naturalist would by this means, besides knowing the outside of the shell, be better acquainted with its internal characters than he otherwise could be, and the lady would have a pleasure in comparing the beauties of the shell, in its wrought state, to its coarse appearance as nature gives it. How many elegancies in this part of the creation must be wholly lost to us, if it were not for the assistance of an art of this kind! Many shells in their native state are like rough diamonds; and we can form no just idea of their beauties till they have been polished and wrought into form.

Though the art of polishing shells is a very valuable one, yet it is very dangerous to the shells; for without the utmost care, the means used to polish and beautify a shell often wholly destroy it. When a shell is to be polished, the first thing to be examined is whether it have naturally a smooth surface, or be covered with tubercles or prominences.

A shell which has a smooth surface, and a natural dull polish, need only be rubbed with the hand, or with a piece of chamoy leather, with some tripoli, or fine rotten stone, and will become of a perfectly bright and fine polish. Emery is not to be used on this occasion, because it wears away too much of the shell. This operation requires the hand of an experienced person, that knows how superficial the work must be, and where he is to stop; for in many of these shells the lines are only on the surface, and the wearing away ever so little of the shell defaces them. A shell that is rough, foul, and crusty, or covered with a tartareous coat, must be left a whole day steeping in hot water: when it has imbibed a large quantity of this, it is to be rubbed with rough emery on a slick, or with the blade of a knife, in order to get off the coat. After this, it may be dipped in diluted aquafortis, spirit of salt, or any other acid; and after remaining a few moments in it, be again plunged into common water. This will add greatly to the speed of the work. After this it is to be well rubbed with linen cloths, impregnated with common soap; and when by these several means it is made perfectly clean, the polishing is to be finished with fine emery and a hair-brush. If after this the shell when dry appears not to have so good a polish as was desired, it must be rubbed over with a solution of gum arabic; and this will add greatly to its gloss, without doing it the smallest injury. The gum-water must not be too thick, and then it gives no sensible coat, only heightening the colours. The white of an egg answers this purpose also very well; but it is subject to turn yellow. If the shell has an epidermis, which will by no means admit the polishing of it, it is to be dipped several times in diluted aquafortis, that this may be eaten off; and then the shell is to be polished in the usual way with putty, fine emery, or tripoli, on the hair of a fine brush. When it is only a pellicle that hides the colours, the shells must be steeped in hot water, and after that the

Shells. Skin worked off by degrees with an old file. This is the case with several of the cylinders, which have not the natural polish of the rest.

When a shell is covered with a thick and fatty epidermis, as is the case with several of the muscles and tellines; in this case aquafortis will do no service, as it will not touch the skin: then a rough brush and coarse emery are to be used; and if this does not succeed, seal-skin, or, as the workmen call it, fish-skin and rub-mice-stone, are to be employed.

When a shell has a thick crust, which will not give way to any of these means, the only way left is to plunge it several times into strong aquafortis, till the stubborn crust is wholly eroded. The limpets, auris marina, the helmet-shells, and several other species of this kind, must have this sort of management; but as the design is to show the hidden beauties under the crust, and not to destroy the natural beauty and polish of the inside of the shell, the aquafortis must be used in this manner: A long piece of wax must be provided, and one end of it made perfectly to cover the whole mouth of the shell; the other end will then serve as a handle, and the mouth being stopped by the wax, the liquor cannot get in to the inside to spoil it: then there must be placed on a table a vessel full of aquafortis, and another full of common water.

The shell is to be plunged into the aquafortis; and after remaining a few minutes in it, is to be taken out, and plunged into the common water. The progress the aquafortis makes in eroding the surface is thus to be carefully observed every time it is taken out: the point of the shell, and any other tender parts, are to be covered with wax, to prevent the aquafortis from eating them away; and if there be any worm-holes, they also must be stopped up with wax, otherwise the aquafortis would soon eat through in those places. When the repeated dippings into the aquafortis show that the coat is sufficiently eaten away, then the shell is to be wrought carefully with fine emery and a brush; and when it is polished as high as can be by this means, it must be wiped clean, and rubbed over with gum-water or the white of an egg. In this sort of work the operator must always have the caution to wear gloves; otherwise the least touch of the aquafortis will burn the fingers, and turn them yellow; and often, if it be not regarded, will eat off the skin and the nails.

These are the methods to be used with shells which require but a moderate quantity of the surface to be taken off; but there are others which require to have a larger quantity taken off, and to be uncovered deeper: this is called entirely scaling a shell. This is done by means of a horizontal wheel of lead or tin, impregnated with rough emery; and the shell is wrought down in the same manner in which stones are wrought by the lapidary. Nothing is more difficult, however, than the performing this work with nicety: very often shells are cut down too far by it, and wholly spoiled; and to avoid this, a coarse vein must be often left standing in some place, and taken down afterwards with the file, when the cutting it down at the wheel would have spoiled the adjacent parts.

After the shell is thus cut down to a proper degree, it is to be polished with fine emery, tripoli, or rotten stone, with a wooden wheel turned by the same machine

as the leaden one, or by the common method of working with the hand with the same ingredients. When a shell is full of tubercles, or protuberances, which must be preserved, it is then impossible to use the wheel: and if the common way of dipping into aquafortis be attempted, the tubercles being harder than the rest of the shell, will be eat through before the rest is sufficiently scaled, and the shell will be spoiled. In this case, industry and patience are the only means of effecting a polish. A camel's-hair pencil must be dipped in aquafortis; and with this the intermediate parts of the shell must be wetted, leaving the protuberances dry: this is to be often repeated; and after a few moments the shell is always to be plunged into water to stop the erosion of the acid, which would otherwise eat too deep, and destroy the beauty of the shell. When this has sufficiently taken off the foulness of the shell, it is to be polished with emery of the finest kind, or with tripoli, by means of a small flick, or the common polishing-stone used by the goldsmiths may be used.

This is a very tedious and troublesome thing, especially when the echinated oysters and murexes, and some other such shells, are to be wrought: and what is worst of all is, that when all this labour has been employed, the business is not well done; for there still remain several places which could not be reached by any instrument, so that the shell must necessarily be rubbed over with gum-water or the white of an egg, afterwards, in order to bring out the colours and give a gloss; in some cases it is even necessary to give a coat of varnish.

These are the means used by artists to brighten the colours and add to the beauty of shells; and the changes produced by polishing in this manner are so great, that the shell can scarcely be known afterwards as not to be the same it was; and hence we hear of new shells in the cabinets of collectors, which have no real existence as separate species, but are shells well known, disguised by polishing. To caution the reader against errors of this kind, it may be proper to add the most remarkable species thus usually altered.

The onyx-shell or volute, called by us the purple or violet-tip, which in its natural state is of a simple pale brown, when it is wrought slightly, or polished with just the superficies taken off, is of a fine bright yellow; and when it is eaten away deeper, it appears of a fine milk-white, with the lower part bluish: it is in this state that it is called the onyx-shell; and it is preferred in many cabinets in its rough state, and in its yellow appearance, as different species of shells.

The violet shells, so common among the curious, is a species of porcelain, or common cowry, which does not appear in that elegance till it has been polished; and the common auris marina shows itself in two or three different forms, as it is more or less deeply wrought. In its rough state it is dusky and coarse, of a pale brown on the outside, and pearly within; when it is eaten down a little way below the surface, it shows variegations of black and green; and when still farther eroded, it appears of a fine pearly hue within and without.

The nautilus, when it is polished down, appears all over of a fine pearly colour; but when it is eaten away but to a small depth, it appears of a fine yellowish colour with dusky hairs. The burgau, when entirely cleared of its coat, is of the most beautiful pearl-colour.

lour; but when but slightly eroded, it appears of a variegated mixture of green and red; whence it has been called the parroquet shell. The common helmet-shell, when wrought, is of the colour of the finest agate; and the muscles, in general, though very plain shells in their common appearance, become very beautiful when polished, and show large veins of the most elegant colours. The Persian shell, in its natural state, is all over white, and covered with tubercles; but when it has been ground down on a wheel, and polished, it appears of a grey colour, with spots and veins of a very bright and highly polished white. The limpets, in general, become very different when polished, most of them showing very elegant colours; among these the tortoise-shell limpet is the principal; it does not appear at all of that colour or transparency till it has been wrought.

That elegant species of shell called the turquil-chama, which has deceived so many judges of these things into an opinion of its being a new species, is only a white chama with a reticulated surface; but when this is polished, it loses at once its reticular work and its colour, and becomes perfectly smooth, and of a fine bright yellow. The violet-coloured chama of New England, when worked down and polished, is of a fine milk-white, with a great number of blue veins, disposed like the variegations in agates.

The ass-ear shell, when polished after working it down with the file, becomes extremely glossy, and obtains a fine rose-colour all about the mouth. These are some of the most frequent among an endless variety of changes wrought on shells by polishing; and we find there are many of the very greatest beauties of this part of the creation which must have been lost but for this method of searching deep in the substance of the shell for them.

The Dutch are very fond of shells, and are very nice in their manner of working them: they are under no restraint, however, in their works; but use the most violent methods, so as often to destroy all the beauty of the shell. They file them down on all sides, and often take them to the wheel, when it must destroy the very characters of the species. Nor do they stop at this: but, determined to have beauty at any rate, they are for improving upon nature, and frequently add some lines and colours with a pencil, afterwards covering them with a fine coat of varnish, so that they seem the natural lineations of the shell: the Dutch cabinets are by these means made very beautiful, but they are by no means to be regarded as instructors in natural history. There are some artificers of this nation who have a way of covering shells all over with a different tinge from that which nature gives them; and the curious are often enticed by these tricks to purchase them for new species.

There is another kind of work bestowed on certain species of shells, particularly the nautilus; namely, the engraving on it lines and circles, and figures of stars, and other things. This is too obvious a work of art to suffer any one to suppose it natural. Buonani has figured several of these wrought shells at the end of his work; but this was applying his labour to very little purpose; the shells are spoiled as objects of natural history by it, and the engraving is seldom worth any thing.— They are principally done in the East Indies.

Shells are subject to several imperfections; some of which are natural and others accidental. The natural defects are the effect of age, or sickness in the fish. The greatest mischief happens to shells by the fish dying in them. The curious in these things pretend to be always able to distinguish a shell taken up with the fish natural and alive from one found on the shores: they call the first a living, the second a dead shell; and say that the colours are always much fainter in the dead shells. When the shells have lain long dead on the shores, they are subject to many injuries, of which the being eaten by sea-worms is not the least: age renders the finest shells livid or dead in their colours.

Besides the imperfections arising from age and sickness in the fish, shells are subject to other deformities, such as morbid cavities, or protuberances, in parts where there should be none. When the shell is valuable, these faults may be hid, and much added to the beauty of the specimen, without at all injuring it as an object of natural history, which should always be the great end of collecting these things. The cavities may be filled up with mastic, dissolved in spirit of wine, or with singlafs: these substances must be either coloured to the tinge of the shell, or else a pencil dipped in water-colours must finish them up to the resemblance of the rest; and then the whole shell being rubbed over with gum-water, or with the white of an egg, scarce any eye can perceive the artifice: the same substances may also be used to repair the battered edge of a shell provided the pieces clipped off be not too large. And when the excrescences of a shell are faulty, they are to be taken down with a fine file. If the lip of a shell be so battered that it will not admit of repairing by any cement, the whole must be filed down or ground on the wheel till it become even.

Fossil Shells. Those found buried at great depths in the earth.

Of these some are found remaining almost entirely in their native state, but others are variously altered by being impregnated with particles of stone and of other fossils; in the place of others there is found mere stone or spar, or some other native mineral body, expressing all their lineaments in the most exact manner, as having been formed wholly from them, the shell having been first deposited in some solid matrix, and thence dissolved by very slow degrees, and this matter left in its place, on the cavities of stone and other solid substances, out of which shells had been dissolved and washed away, being afterwards filled up less slowly with these different substances, whether spar or whatever else: these substances, so filling the cavities, can necessarily be of no other form than that of the shell, to the absence of which the cavity was owing, though all the nicer lineaments may not be so exactly expressed. Besides these, we have also in many places masses of stone formed within various shells; and these having been received into the cavities of the shells while they were perfectly fluid, and having therefore nicely filled all their cavities, must retain the perfect figures of the internal part of the shell, when the shell itself should be worn away or perished from their outside. The various species we find of these are, in many genera, as numerous as the known recent ones; and as we have in our own island not only the shells of our own shores, but those of many other very distant ones, so we have also

Shells also many species, and those in great numbers, which are in their recent state, the inhabitants of other yet unknown or unsearched seas and shores. The cockles, mussels, oysters, and the other common bivalves of our own seas, are very abundant: but we have also an amazing number of the nautilus kind, particularly of the nautilus grecorum, which though a shell not found living in our own or any neighbouring seas, yet is found buried in all our clay-pits about London and elsewhere; and the most frequent of all fossil shells in some of our counties are the conche anomie, which yet we know not of in any part of the world in their recent state. Of this sort also are the cornua ammonis and the gryphite, with several of the echinite and others.

The exact similitude of the known shells, recent and fossil, in their several kinds, will by no means suffer us to believe that these, though not yet known to us in their living state, are, as some have idly thought, a sort of lusus nature. It is certain, that of the many known shores, very few, not even those of our own island, have been yet carefully searched for the shell-fish that inhabit them; and as we see in the nautilus grecorum an instance of shells being brought from very distant parts of the world to be buried here, we cannot wonder that yet unknown shores, or the unknown bottoms of deep seas, should have furnished us with many unknown shell-fish, which may have been brought with the rest; whether that were at the time of the general deluge, or the effect of any other catastrophe of a like kind, or by whatever other means, to be left in the yet unhardened matter of our stony and clayey strata.