Head distinct from the body, bearing the lips or jaws.

The head, or the anterior part of the body, on which zoologists have bestowed that denomination, possesses more or less freedom of motion, and, on the dorsal aspect, supports either tentacula or eyes, frequently both. The animals of this division exhibit so many modifications of form and structure, in all the series of organs, that the positive characters which they possess in common are few in number. They easily admit, therefore, of subdivision into inferior groups, which exhibit well marked characters of distinction. Two of these groups occupy a primary rank, and admit of the others being included under them as subordinate sections. In the first of these, the animals are all inhabitants of the water, and perform their progressive motion through that element by organs fitted for swimming. They are destitute of any ventral disc on which to crawl. In the second group, including animals which inhabit the land, as well as those which live in fresh water and in the sea, progressive motion is performed by means of crawling along the surface of objects, the body resting on a ventral disc, termed a foot.

The organs of motion are situated near the anterior extremity of the body, and either consist of flexible tentacula, or membranaceous expansions. All the species reside in the sea. They are nearly of the same specific gravity with the surrounding fluid, in which they float about, having their motions in a great measure regulated by its changes. It is however probable, that, by means of some contractile movements, they are capable of varying their density, and of rising or sinking in the water. They swim slowly, even with their utmost efforts. M. Cuvier has distributed the animals of this subdivision into two classes, which he has termed Cephalopoda and Pteropoda.

Fins in the form of tentacula, surrounding the mouth.

Cephalopodous animals consist of a body and head. The body is surrounded by a sac or tunic, closed posteriorly, and in part open anteriorly, for the orifices of the several organs. This tunic differs greatly in its texture, and is strengthened internally by testaceous or corneous productions, or externally by means of a spiral shell. The neck is more or less distinct from the sac. The head is flattened into a disc, in the centre of which is the mouth, and, towards the margin, the tentacula take their rise. The two Linnæan genera, Nautilus and Sepia, comprehend all the animals which are at present considered as belonging to this class.

Furnished with a multilocular shell.

This order is involved in the greatest obscurity. None of the recent species have been subjected to an accurate examination, so that their connection with the order sepiacea may still be considered doubtful. Enough is known of the animals of two of the genera, to furnish some hints for those who are fond of classifying animals from their analogies. These genera are Spirula and Nautilus.

In the Spirula, the shell, which is concealed under the skin of the back, is spiral, with the whorls separate, the mouth orbicular, the chambers perforated by a pipe, and the last cell produced into a tube. The position and use of this terminal tube are unknown. The S. vulgaris is the most common species, and inhabits the seas in the West Indies. In the restricted genus Nautilus, the shell is supposed to be external, and the body of the animal to be lodged in the last chamber, and to be fixed by a ligament which descends into the central pipe. In the shell itself, the turns of the spire are contiguous, and the last whorl embraces the others on the sides.

Mollusca. The N. pompilus of Rumphius is the only species in which the animal has been detected.

The other genera which have been formed in this order depend exclusively on the characters furnished by the shells, and the resemblance which these bear to the preceding genera constitutes all their claim to be included in the present order. (See CONCHOLGY, Genus 18, Nautilus.)

II. Order.

SEPIACEA.

Destitute of a multilocular shell.

The sac is strengthened by horny or testaceous plates, unless where the habits of the animal render such support unnecessary.

1. HEAD SURROUNDED WITH EIGHT ARMS AND TWO FEET.

The two feet are nearly similar in their structure to the arms, or tentacula, but considerably larger in their dimensions. They have their organ on the ventral side of the mouth, between that organ and the funnel. The suckers are pedunculated, with their margin strengthened by a corneous ring, furnished with teeth. The sac is furnished with fin-like expansions, and strengthened internally by corneous or testaceous ribs or plates. The head is divided from the sac on all sides by a neck. The margin of the anus is surrounded with tentacula.

Genus, Sepia.—The sac is furnished on each side throughout its whole length with a narrow fin.

The suckers are irregularly scattered on the arms and feet. The back is strengthened by a complicated calcareous plate, lodged in a peculiar cavity. This plate has been long known in the shop of the apothecary, under the name Cuttle-fish bone, and belongs to the species termed S. officinalis.

Genus, Loligo.—Calamary. Sides of the sac only furnished partially with fins.

The suckers are disposed on the arms and feet in a double row. The dorsal plate is flexible and corneous, imbedded in the substance of the sac, and is multiplied with years. The Sepia loligo of Lin. is the type of the genus.

Dr Leach has described three new species of the genus Loligo, which were collected by Mr Cranch during the voyage to the Congo, in the unfortunate expedition under the direction of Captain Tuckey. These species belong to a group which have the suckers produced into hooked processes. In two of these species, L. leptura and Smithii, the suckers on the arms, as well as the feet, are produced into hooks, while, in one species, L. Banksii, the feet only are armed with hooks.

The same distinguished naturalist has instituted a new genus nearly allied to Loligo, from two species collected during the same voyage. The following characters are assigned to it.

“Genus, Cranchia.—Body oval, sack-shaped;

fins approximating, their extremities free; neck with a frenum behind, connecting it with the sack, and with two other frena, connecting it with the sack before.

“Sp. 1. Cranchia scabra.—Sack rough, with hard rough tubercles.

“Sp. 2. Cranchia maculata.—Sack smooth, beautifully mottled with distant ovate spots.”*

HEAD SURROUNDED WITH EIGHT ARMS WITHOUT FEET.

The suckers have soft margins. The sac is destitute of fin-like expansions, and is either simple or strengthened in the interior by two short corneous processes. The head is united with the sac behind, without the intervention of a neck.

Arms all equal in Size.

Genus, Octopus.—Suckers arranged in a double row.

The suckers are sessile. The oviduct is double. The margin of the anus is simple. The Sepia octopodia of Lin. is the type of the genus.

Genus, Eledona.—Suckers on the arms disposed in a single row.

M. Lamarck has figured and described two species of this genus, in the Mem. de la Soc. d'Hist. Nat. One of these is a native of the Mediterranean, and is remarkable for giving out an odour like musk.

Arms Unequal.

Genus, Ocythoe.—Two of the arms at their inner extremities furnished with membranaceous expansions.

In this genus, which was instituted by M. Rafinesque, the suckers are in a double row, and supported on footstalks. In the specimens of the Ocythoe Cranchii, procured during the expedition to the Congo, Dr Leach observed “four oblong spots on the inside of the tube, resembling the surfaces for the secretion of mucus, two inferior and lateral, and two superior, larger, and meeting anteriorly. On the rim of the sac, immediately above the branchiae, on each side, is a small, short, fleshy tubercle, which fits into an excavation on the opposite side of the sac.” Phil. Trans. 1817.

This animal was long considered as the fabricator of the shell termed Argonauta or Paper Nautilus. The observations, however, of Mr Cranch, the Zoologist to the Congo Expedition, have demonstrated that the shell is merely the temporary residence of this animal, which it quits at pleasure. “On the 13th of June,” says Dr Leach, “he placed two living specimens in a vessel of sea-water; the animals very soon protruded their arms, and swam on and below the surface, having all the actions of the common Polyopus (octopus) of our seas; by means of their suckers, they adhered firmly to any substance with which they came in contact, and when sticking to the sides

* Narrative of an Expedition to Explore the River Zaire, usually called the Congo, in South Africa, in 1816, under the direction of Captain J. K. Tuckey, R. N. London, 1818, p. 410.

Mollusca. of the basin, the shell might easily be withdrawn from the animal. They had the power of completely withdrawing within the shell, and of leaving it entirely. One individual quitted its shell, and lived several hours swimming about, and showing no inclination to return into it; and others left the shells as he was taking them up in the net. They changed colour, like other animals of the Class Cephalopoda; when at rest the colour was pale flesh-coloured, more or less speckled with purplish; the under parts of the arms were bluish-grey; the suckers whitish." The specimens which furnished an opportunity for making the preceding observations were met with in the Gulf of Guinea, and afterwards on the voyage, swimming in a small argonauta, on the surface of the sea. The reader, who is desirous of farther information on this subject, may consult Dr Leach's Observations on the Genus Ocythoe of Rafinesque, and Sir E. Home on the Distinguishing Characters between the Ova of the Sepia, and those of the Vermes Testacea that Live in Water, in the Philosophical Transactions for 1817, Art. xxii. and xxiii. (both of which are added to the appendix of Captain Tuckey's Narrative), and a paper by Mr Say on the Genus Ocythoe in the Phil. Trans. 1819, Art. vii.

Fins formed of membranaceous expansions.

M. Cuvier, whose valuable papers on the Genera Clio, Pneumodermon, and Hyalea, include nearly all the accurate information which naturalists possess, divides the animals of this class into cephalous and accephalous. In the latter division he places the genus Hyalea. The head of the animal of this genus, with its inferior neck, may, however, be sufficiently recognized to remove all doubt of its existence.

The characters which may be employed in the classification of this group are numerous; but the influence which their different forms exercise on the habits of the species is still unknown. The following disposition of the genera, though it has no claims to a natural division, may be useful to the student in his investigations.

Genus, Limacina.—Posterior extremity of the body covered by a spiral shell.

The shell, which is very tender, makes one turn and a half, is flat on one side, with a large pillar cavity on the other. The fins are two in number, seated on each side of the neck. When the animal swims, the head with the fins are protruded.

This genus was instituted by Cuvier, for the reception of the Clio helicina of Captain Phipps, or Argonauta arctica of Fabricius. According to Mr Scoresby, it is found in great quantities near the coast of Spitzbergen.

Genus, Hyalea.—Posterior extremity of the body protected by two connected shelly valves.

The Hyalea tridentata, the best known species of the genus, was first noticed by Forskael, in his Descriptiones Animalium, p. 124, as an anomaly, and inhabiting the Mediterranean. The same species was

likewise taken in abundance in the Gulf of Guinea, by the expedition under Captain Tuckey.

Genus, Pneumodermon.—Head with two bundles of tentacula.

The body is oval, with a narrow neck, and a fin on each side. The mouth is nearly terminal, furnished on each side with a fleshy lip, and beneath, with a fleshy chin. The tentacula consist each of a filament, with a tubercle at the end, pierced by a small hole, and considered as exercising the office of a sucker. M. Cuvier has figured and described the only known species, which he terms Pneumodermon Peronii, the trivial name being in honour of the discoverer, M. Peron.

Genus, Clio.—Body ovate, with the tunic elongated and membranaceous.

The head is divided into two lobes, the summits of which are furnished with tentacula. The existence of eyes has not been ascertained. The Clio Borealis, a native of the Arctic Seas, is the type of the genus.

Genus, Cleodora.—Body covered with a triangular pyramidal tunic.

The fins are membranaceous. The mouth is situated between them, and is furnished with a semi-circular lip. This genus was instituted by Peron, for the reception of the Clio of Brown. The C. pyramidata is the best ascertained species. Brown's Jamaica, p. 386, Tab. xliii. f. 1. Two other species were taken by the Congo expedition in S. Lat. $2^\{\backslash circ\}\; 14\text{'}$, and E. Long. $9^\{\backslash circ\}\; 55\text{'}$, and S. Lat. $2^\{\backslash circ\}\; 41\text{'}$ E. Long. $9^\{\backslash circ\}\; 16\text{'}$, "both having a spinous process on each side of their shell, near its opening. One species is beautifully sulcated transversely, and the other but slightly so." Tuckey's Narrative, p. 412.

Genus, Cymbulia.—Tunic cartilaginous and trough-shaped.

The fin is single, divided into three lobes, one of which is small, with two tubercles, and a minute fleshy beard. This genus was instituted by Peron, in Annales du Museum, T. XV. T. iii. f. 10, 11.

This is one of the most extensive groups of Molluscos animals. The marks by which it is distinguished are well defined, and the external and internal characters of the species have been successfully illustrated.

The Gasteropoda may be considered as having the body protected dorsally by the cloak, and ventrally by the foot. The cloak is either continuous, and usually more or less arched for the reception of the viscera underneath, or it is interrupted by a pro-

Mollusca. jecting bag, in which are contained the principal digestive and reproductive organs. This projecting bag is tapering and spiral, and always protected externally by a shell. When the cloak is continuous, the surface is variously marked, and frequently exhibits a particular portion, more elevated than the rest, in some cases concealing a testaceous plate, which has been termed the shield.

The foot, situate on the ventral surface, and in opposition to the cloak, exhibits a flat soft surface, consisting of interlaced muscular fibres. Its central surface serves as support to the viscera, while externally it constitutes the organ of progressive motion. It is a sucker rather than a foot, and enables the animal to adhere to objects when at rest, and to crawl from one place to another by a succession of adhesions, not unlike the leech. It is also used as a fin in swimming.

By the union of the cloak and foot, laterally and posteriorly, a sac is formed, which is open in front for the protrusion of the neck and head. The line of junction between the cloak and foot is marked, in general, by peculiarities in the condition of the margins of both.

The neck is usually divided from the cloak by a collar, or thickened margin belonging to the latter, or rather to the shield, while in other cases it is continuous. Underneath, the neck is frequently attached to the foot.

The head supports the tentacula and eyes, is free dorsally, but frequently intimately connected with the foot on its ventral side. The portion between the tentacula and the mouth is termed the snout (le muse of the French, and its margin le chaperon). The mouth exhibits various modifications of fleshy lips and corneous jaws. The inside of the cheeks are covered in some species with reflected teeth to aid deglutition. The tongue can scarcely be detected in some of the genera, while in others it is a simple tubercle, or a strap-shaped, spiral organ, armed with transverse rows of teeth. This spiral tongue, where it is fixed to the base of the mouth, is broadest, and there also the spinous processes are strongest. The spiral part is narrowest and softest, and folded up behind the pharynx. M. Cuvier conjectures, and apparently with plausibility, that the spiral portion comes forward into the mouth to act as a tongue, in proportion as the anterior part is worn by use and absorbed. (See his Memoire sur la Vivipare d'eau douce, p. 12.)

The organs of respiration exhibit the two modifications of lungs and gills, and enable us to divide the gasteropoda into two classes, which we have termed Pulmonifera and Branchifera. M. Cuvier appears to have been in some measure aware of the importance of the distinction when he instituted his order Pulmonés, but he afterwards suffered himself to be more influenced by the presence of an operculum, the shape of the aperture of the shell and the supposed separation of the sexes, than by the characters of the respiratory organs.

I. Class.

PULMONIFERA.

The pulmonary cavity is single and lateral. Its

VOL. V. PART II.

orifice is capable of being closed at the will of the animal. The blood-vessels are spread, chiefly on the walls and roof, like delicate net-work.

Mollusca. The reproductive system of the animals of this class exhibits the sexual organs, in general, united in the same individual. Mutual impregnation, however, is necessary. All the species are oviparous. The eggs are either naked, as in the terrestrial genera, or enveloped in a gelatinous mass like the aquatic kinds. The embryo acquires nearly all its members while in the egg, and the shell is of a proportional size previous to hatching. Sir Everard Home, when treating of the distinguishing characters between the ova of the sepia, and those of the vermes testacea, that live in water (Phil. Trans. 1817, p. 297), and when referring to the ova of the vermes testacea, says, "If the shell were formed in the ovum, the process of aerating the blood must be very materially interfered with, for this reason, the covering, or shell of the egg, first drops off, and the young is hatched before the shell of the animal is formed; this I have seen take place in the eggs of the garden snail, but in the testacea that live in water, the young requires some defence in the period, between the egg being hatched and the young acquiring its shell, which is not necessary in those that live on land; for this purpose, the ova are enclosed in chambers of a particular kind." The assertion here made, and founded on a priori considerations, that the shell is not formed until after the egg is hatched, is opposed by every observation which we have been able to make on the subject; and what is more surprising, it is at variance with his own observations on the garden snail, the very example produced in its confirmation. The eggs of a snail laid on 5th August 1773 were hatched on the 20th of that month, and their condition at this time distinctly stated. "On the 20th, the young were hatched, and the shells completely formed." It is much more becoming, in a philosopher, to observe how nature operates, than to pronounce what she must do.

I. Order.

TERRESTRIAL.

The animals of this order reside constantly on the land. When by accident they fall into the water, they appear to be incapable of using their foot as a sucker or as a fin, and die after a few writhings. The species in general prefer moist places, and seldom are very active in dry weather. After a shower they speedily leave their hiding-places, and at this time they may be readily collected. The eggs are hatched on land.

1. Subdivision.

Cloak and foot parallel, and containing the viscera between them.

In this group are included those animals denominated slugs in this country. They possess four retractile tentacula, of unequal length. The eyes are two in number, in the form of black points, seated at the tips of the posterior tentacula.

1. Tribe.

Cloak furnished with a shield.

The shield is, in general, strengthened internally by a deposition of earthy matter, in the form of grains, or a plate.

In this group, the shield is placed nearer the head than the tail. It contains four genera, two of which have compound tails, or furnished with peculiar organs, while in the remaining genera the tails are simple.

Genus, Arion.—A mucous orifice at the termination of the cloak.

This genus has been recently instituted by M. le Baron D'Audebard De Ferrussac, in his Histoire Naturelle Générale et Particulièrè du Mollusques Terrestres et Fluviales, folio, Paris, 1819, 3e liv. p. 53. The species of which it consists were formerly confounded with those which now constitute the restricted genus Limax. It differs, however, in possessing the mucous pore, in the pulmonary orifice being near the anterior margin of the shield, with the sexual orifice underneath, and in the soft state of the calcareous matter in the shield. The author now quoted has described four species, and illustrated their characters by beautiful and expressive figures. The Limax ater (together with its variety rujus) of British writers may be regarded as the type of the genus.

Genus, Plectrophorus.—A conical protuberant shell at the termination of the cloak.

This genus, likewise instituted by M. Ferrussac, nearly resembles the preceding in form. Three species have been described and figured, which, however, differ remarkably from one another.

The genera of this group have neither a terminal mucous orifice nor shell.

Genus, Limax.—Pulmonary orifice near the posterior margin of the shield.

This genus, as now restricted by M. Ferrussac, differs from the Arion in the absence of the caudal mucous pore, the position of the pulmonary cavity, and the orifice of the sexual organs placed under the superior right tentaculum. The calcareous matter of the shield is more solid, and appears as a shelly plate. Six species have been described and figured.

The Limax cinereus of Lister is the type of the genus.

Genus, Limacellus.—Pulmonary orifice near the anterior margin of the shield.

This genus was instituted by M. de Blainville, in the Journal de Physique, December 1817, p. 442, pl. 11, f. 5, nov. His observations were made on a specimen in a shrivelled state, preserved in spirits of wine, which was communicated to him from Dr Leach of the British Museum. Its history is, therefore, necessarily imperfect. The animal is rounded before and pointed behind, and dorsally protuberant. The whole body is smooth, soft, and of a greyish white colour. The shield, which adheres on all sides, is destitute of any shelly plate. It is notched near its anterior margin, at the opening of the pulmonary cavity. The foot is broad, and separated

from the cloak by a slight fold, which, on the right side, forms a groove, leading from the base of the right tentaculum to the posterior extremity of the body. It is inferred from this appearance, that the sexual organs are disjoined, the female parts being seated in the tail, while the male organs occupy the ordinary position. The only species, Limacellus lactescens, is supposed to have been brought from the Antilles.

In this group, the shield is placed nearer to the tail than in the preceding, and is fortified internally with a subs spiral plate. It contains one genus.

Genus, Parmacella.—Posterior extremity of the shield containing the shell.

The pulmonary cavity is placed underneath the shell of the shield. This arrangement occasions a corresponding posterior position to the heart. Along the back, from the shield to the head, are three grooves, the middle one of these is double. The shield itself adheres only at the posterior portion, the anterior part being free. The internal structure is similar to the slugs. The only marked difference, indeed, consists in two conical appendages of the sexual cavity, by which there is an approach to the Helices.

The Parmacella Olivieri is the only known species, and was first described, and its structure unfolded, by M. Cuvier. It was brought from Mesopotamia by M. Olivier.

In this tribe, the pulmonary cavity is situate near the tail.

Genus, Testacella.—Pulmonary cavity underneath the shell.

The vent and pulmonary cavity are from the position of the protecting shell, on which they are dependent, nearly terminal. The foot extends on each side beyond the body. From the manner in which the blood is aerated, the auricle and ventricle are placed longitudinally, the latter being anterior.

This genus at present consists of three species. One of these, T. haliotoides, is a native of France and Spain. It lives in the soil, and feeds on the earthworm. Another species, the T. Maugei, was first observed at Teneriffe by M. Mauge. It has been figured in the splendid work on the Mollusca, by Ferrussac, already referred to, Tab. vii. f. 10—12, from specimens found in the botanical garden of Bristol, and communicated by Dr Leach. It has been conjectured, that the British animals may have been introduced along with plants from Teneriffe. The third species, T. ambiguus, is established on the doubtful authority of a shell in the collection of M. Lamarck.

Genus, Veronicellus.—Cloak fortified posteriorly by an internal shelly plate. Tentacula four.

This genus was instituted by M. Blainville for the reception of the V. lavis, established from a specimen preserved in spirits, belonging to the British Museum, and communicated by Dr Leach. It is figured

Mollusca. by Ferrussac, Tab. vii. Fig. 6, 7. The body is somewhat pointed before, and rounded behind. The cloak is large; the foot rather narrow, and plaited on the edges. The opening to the pulmonary cavity is situated on the right side posteriorly, under the shell. A little in advance of this is another opening, in the middle of which is the funnel-shaped aperture of the anus. The sexual organs are united, and placed at the base of the right tentaculum.

It is not improbable, according to Ferrussac, that the Limax nudus cinereus terrestris of Sloane (Jam. ii. p. 190, Tab. cxxxiii, f. 2, 3), may belong to this genus, or rather, that the individual brought home by Sloane may have been the identical specimen submitted to M. Blainville's examination.

Genus, Onchidium.—Cloak tuberculated. Snout enlarged and emarginate. Tentacula two in number, with eyes at the tips.

This genus was instituted by Dr Buchanan, in Lin. Trans. Vol. V. p. 182, for the reception of a species which he found in Bengal, on the leaves of Typha Elephantina. It is not, according to this naturalist, "like many others of the worm kind, an hermaphrodite animal; for the male and female organs of generation are in distinct individuals. I have not yet perceived any mark to distinguish the sexes, while they are not in copulation, as in both, the anus and sexual organs are placed in a perforation (cloaca communis), in the under part of the tail, immediately behind the foot; but during coition, the distinction of sexes is very evident, the penis protruding to a great length, considering the size of the animal."

2. Subdivision.

Cloak and foot parallel; the viscera contained in a spiral dorsal protuberance, protected by a shell.

This group includes the animals usually denominated SNAILS. They bear a very close resemblance to the slugs. The shield, however, has a thickened margin in front, destined to secrete the matter of the shell. In the part corresponding with the centre of the shield in the slugs there is (as Cuvier has characteristically termed it) a natural rupture, through which the viscera are protruded into a conical bag twisted spirally. In this bag are contained the principal viscera, the liver occupying its extremity. The body of the animal is attached to the pillar of the shell by a complicated muscle, which shifts its place with the growth of the animal. The mouth is furnished above with a thin-arched corneous mandible, notched on the edges. The whole body, including the foot and head, are, in general, capable of being withdrawn into the cavity of the shell. In one genus, the aperture is closed by a lid.

1. Tribe.

The foot is furnished with a lid or operculum, for closing the mouth of the shell when the animal withdraws itself into the cavity.

Genus, Cyclostoma.—Aperture of the shell circular.

The tentacula are linear and subretractile. The primary ones have subglobular, highly-polished extremities, considered by Montague as the eyes. The

true eyes, however, are placed at the exterior base of the large tentacula, and are elevated on tubercles, which are the rudiments of the second pair.

The aperture of the pulmonary cavity is situated on the neck. The sexes are likewise separate; the penis of the male being large, flat, and muscular. The mouth is formed into a kind of proboscis, and the upper lip is deeply emarginate. The Turbo elegans of British conchologists is the type of the genus.

2. Tribe.

Foot destitute of a lid.

A. Aperture of the shell with a thickened margin.

In all this division, the margin of the shell, while the animal is young, is thin; but upon reaching a certain period, it becomes thick, and bordered with a ring, after which, there is no increase of size.

1. Last formed Whorl of the Shell greatly larger than the penultimate one.

Genus, Helix.—Snail. Aperture of the shell lunulated; the width and length nearly equal.

The snails differ from the slugs chiefly in the organs of reproduction. The vagina, previous to its termination in the sexual cavity, is joined by the canal of the vesicle, and by two ducts, each proceeding from a bundle of multifid vesicles. Each bundle consists of a stem or duct, and numerous branches, with blunt terminations. These organs secrete a thin milky fluid, the use of which is unknown.

The species belonging to this genus are numerous, and exhibit, in the form, the markings, and the coverings of the shell, numerous characters for their subdivision.

Genus, Bulimus.—Aperture of the shell longer than broad.

The structure of the animals of this genus has not been determined; but analogy would lead us to conclude, that it is similar to the snails. While the shells of the Helix are globose, those of Bulimus are turrit.

2. Last Whorl nearly of the same size as the penultimate one, or even less.

The genera of this group are already noticed sufficiently in detail, in the article CONCHIOLOGY of this Supplement, under the 27 genus, Turbo.

B. Aperture of the shell destitute of thickened margin.

There is in this group no certain indication of maturity or stationary growth.

1. Mouth of the Shell at the Pillar entire.

Genus, Vitrina.—Margin of the shield double.

The upper fold of the shield is divided into several lobes, which are capable of being reflected over the surface of the shell. The shell itself is not capable of containing the whole body of the animal. The Helix pellucida of Muller is the type of the genus. It is a common British species, and was hastily regarded by Montague as the fry of the Helix lucida.

Genus, Succinea.—Termination of the pillar rounded.

The Helix putris of British writers is the type of the genus.

Genus, Achatina.—The termination of the pillar truncated.

The Buccinum acicula of Muller, a native of England, belongs to this genus; and likewise the Helix octona of Linnaeus, erroneously considered as a native of Britain.

The aquatic pulmoniferous gastropoda have their residence constantly in the water. They possess two tentacula only. These are usually flattened, incapable of being withdrawn, and having eyes at the internal base. The food consists of aquatic plants. Respiration can only take place at the surface of the water, to which the animals occasionally ascend, to expel from the pulmonary cavity the vitiated air, and replenish it with a fresh supply. The sexes are united. The spawn, which is in the form of a rounded gelatinous mass, containing many ova, is deposited on aquatic plants under water. Previous to hatching, the foetus must be aerated by means of some branchial arrangement.

Body protected externally by a shell.

The animals belonging to this subdivision bear a very close resemblance to the snails, in the structure of their body, and the form of their shell.

The protecting shell spirally twisted.

Genus, Lymnaea.—Aperture of the shell having the right lip joined to the left at the base, and folding back on the pillar.

The tentacula are lanceolate and depressed. The mouth is furnished with three jaws; the lateral ones simple; the upper one crescent-shape, and emarginate. The male and female organs, though intimately connected, internally, have their external orifices separated to a considerable distance, the former issuing under the right tentaculum, the latter at the pulmonary cavity. There are several species natives of Britain.

Genus, Physa.—Pillar-lip destitute of a fold.

The external appearance of the animal is similar to the Lymnaea; but the margin of the cloak is loose, divided into lobes, and capable of being reflected over the surface of the shell near the mouth. This genus was instituted by Draparnaud. The Bulla fontinalis of British authors is regarded as the type of the genus.

Genus, Aplexa.—Pillar-lip, with a fold.

This genus was instituted by us for the reception of the Bulla hypnorum and rivalis of British writers. The shell is more produced than in the physa. The cloak of the animal is incapable of being reflected on the shell, and its margin is destitute of lobes.

The spires revolve in nearly the same horizontal line. The tentacula are long, and filiform.

Genus, Planorbis.—Cavity of the shell entire.

This is another sinistral genus; the vent, pulmonary cavity, and sexual organs, being on the left, and the heart on the right side. The P. corneus, the type of the genus, pours forth, when irritated, a purple fluid from the sides, between the foot and the margin of the cloak.

Genus, Segmentina.—Cavity of the shell divided.

Externally, the shell appears similar to planorbis; but internally, it is divided by testaceous transverse partitions into several chambers, which communicate with each other by triradiated apertures. It is uncertain whether the animal is to be considered as dextral or sinistral. This genus was instituted by us several years ago, for the reception of the Nautilus lacustris of Lightfoot, first described and figured in Phil. Trans. Vol. LXXVI. p. 160. Tab. i. f. 1. 8.

Shell simply conical.

Genus, Ancylus.—Foot short, elliptical.

The tentacula are short, compressed, and a little truncated. This genus was formed by Geoffroy, and includes the Patella lacustris and oblonga of British conchologists.

Body destitute of the external protection of a shell.

Genus, Peronia.—Head with two long retractile tentacula. The snout is divided into two broad appendages. Between the tentacula, towards the right side, is the opening for the penis. The anus is terminal, immediately above which is the entrance to the pulmonary cavity; and on the right is the opening to the female organs, from which a groove runs towards the right lobe of the snout.

This genus, which we have named in honour of M. Peron, was referred by Cuvier to the Onchidium of Buchanan, which we have already noticed, and the species termed O. Peronii. It was found creeping upon marine rocks, under water, at the Mauritius, by M. Peron. M. Cuvier conjectures that it breathes free air, and has accordingly inserted it among the Pulmones aquaticus. Some doubts, however, may reasonably be entertained about the truth of this supposition. It would certainly be an unexpected occurrence to find a marine gastropodous mollusca obliged to come to the surface at intervals to respire. It will probably be found that it is truly branchiferous.

The molluscous animals of this class are more numerous than those of the preceding. They chiefly

Mollusca. inhabit the waters of the ocean, a few genera only being met with in fresh water lakes and rivers. The branchiæ which constitute their aerating organs exhibit numerous varieties of form, position, and protection, and furnish valuable characters for their methodical distribution.

The branchiæ are pedunculated, and more or less plumose. They are moveable at the will of the animal, and in general are capable of great alteration of form.

In nearly all the genera the branchiæ are numerous, and distributed regularly over the cloaks or sides.

In many species the back is covered with perforated papillæ, which pour out a mucous secretion. All the species are hermaphrodite, with reciprocal impregnation.

a. Anus situate near the posterior extremity of the back, and surrounded with a fringe of plumose branchiæ.

Genus, Doris.—Oral tentacula two; vent without scales.

The cloak is covered with retractile papillæ, and separated from the foot by a distinct duplicature. Towards its anterior margin are placed the two superior tentacula. These are retractile, surrounded at the base with a short sheath, and supported on a slender stem, having an enlarged compound plicated summit. The neck is short, and above the mouth there is a small projecting membrane, connected at each side with the oral tentacula, which are in general minute, and of difficult detection.

The following species are natives of the British seas: 1. D. Argo; 2. verrucosa; 3. lævis; 4. marginata; 5. nodosa; 6. quadricornis; 7. nigricans.

Genus, Polycera.—Oral tentacula more than two. The branchiæ, when withdrawn, are protected by two scales. The superior tentacula resemble those of the Doris, the oral ones are more numerous, sometimes amounting to six. P. flava and pennigera are British examples.

b. Anus situate on the right side, and unconnected with the branchiæ.

These jaws are in the form of narrow plates, which cut the food by crossing each other like the blades of a pair of scissors.

(1.) Branchiæ disposed along the back or sides, and unconnected with membranaceous expansions.

Genus, Tergipes.—Branchiæ furnished with sheaths at the base.

Mollusca. The branchiæ form a single row on each side, and are qualified to act as suckers. The Limax tergipes of Forskæl, Des. An. p. 99, is the type of the genus. T. maculata, described by Montagu, Lin. Trans. VII. p. 80, T. vii. f. 8, 9, is a British example.

Genus, Tritonia.—Branchiæ destitute of basilar sheaths.

The branchiæ are in the form of plumes, or imbricated productions, placed in a row on each side the back. The tentacula, which are partially retractile, have a sheath at the base. In some of the species there are indications of eyes. The T. arborescens, pinnatifida, and bifida, are examples of British species.

The branchiæ are simple, tapering, or clavate, and disposed in transverse rows on each side. These branchiæ in some species readily fall off, and are capable of swimming about in the water for a short time, as if independent. This is executed by means of minute hairs with which their surface is covered, and which move rapidly, pushing forward the distal extremity.

Genus, Montagua.—Branchiæ in continuous rows across the back.

This genus, which differs from the other not merely in the arrangement of the branchiæ, but in possessing a cluster of short papillæ on the right side, probably connected with the anus, we have ventured to name in honour of the late George Montagu, the well-known author of Testacea Britannica, and of several valuable papers in the Linnean Transactions, on molluscous animals. The two species which may be referred to this genus were detected in Devonshire by this observer. The first, M. longicornis, Lin. Trans. Vol. IX. p. 107. Tab. vii. f. 1, is the type of the genus. The other species, M. carulea, Lin. Trans. Vol. VII. p. 78. Tab. vii. f. 4, 5, is probably the type of another genus.

Genus, Eolida.—Branchiæ interrupted on the back.

This genus, which was instituted by M. Cuvier, includes the following British examples: 1. E. papillosa; 2. plumosa; 3. pedata; 4. purpurascens.

(2.) Branchiæ disposed on lateral membranaceous expansions.

These expansions serve the double purpose of supporting the branchiæ, and acting as fins.

Genus, Scyllæa.—Branchiæ seated dorsally on the fins. Tentacula two.

On each side of the back are two membranaceous expansions, and one on the tail, supporting on their dorsal surface scattered plumose branchiæ. The tentacula are each furnished with a large funnel-shaped sheath. The foot is very narrow, with a mesial groove, used in climbing up the stalks of sea weeds. The mouth is placed at the base of the tentacula, and surrounded with a semicircular lip. The tongue is in the form of a tubercle, with reflected points. The gullet is plaited longitudinally. The stomach is short and cylindrical, with a ring of hard longitudinal scales. The liver consists of six unequal globules, and the bile is poured into the cardiac extremity of the gullet. The Scyllæa pelagica has been long known to naturalists, and appears to

Mollusca. he very common in the equatorial seas, adhering to the stems of the Fucus natans.

Genus, Glaucus.—Branchiæ seated on the margin of the fins. Four simple tentacula.

On each side of the body there are three or four membranaceous expansions, the margins of which are fringed with the simple branchial filaments. This genus was instituted by R. Forster, and the oldest known species, G. radiatus, is figured, Phil. Trans. Vol. LIII. Tab. iii.

(B.) Mouth destitute of corneous jaws.

Genus, Thethys.—Branchiæ forming a row on each side the back, consisting of fringed processes, alternately larger and smaller.

The T. fimbria is the type of the genus, a figure of which, with its anatomical details, is given by M. Cuvier, in his Mémoire sur le Genre Thethys.

2. Body concealed in a Spiral Shell.

This section includes the genus Valvata of Muller, represented by two British species, V. cristata (Helix cristata of Montagu) and V. piscinalis (Turbo fontinalis). These resemble in aspect the aquatic pulmoniferous gastropoda. The branchiæ appear in the form of a feather, with a central stem, and a row of compound branches on each side, decreasing in size from the base to the free extremity. It issues from the neck near the middle, a short way behind the anterior tentacula. Near this plume, but towards the right side, is a single simple filament, like a tentaculum. The anterior tentacula occupy the usual position, are setaceous, and have the eyes placed at the base behind. The spiral shell is capable of containing the body, and the aperture can be closed by a spirally striated operculum attached to the foot. The internal structure is unknown.

B. Branchiæ issuing laterally from between the cloak and foot.

This division includes the orders Cyclo-branchia and Infero-branchia of Cuvier, which we have ventured to bring together, as connected by the common character of the position of the gills.

1. Body protected dorsally by a shelly covering. Cyclobranchia.

a. Shell simple.

Genus, Patella.—Shell entire. Mouth with tentacula.

The species belonging to this genus are numerous, and appear to admit of distribution into sections; the first having the branchial circle complete, the second interrupted.

b. Shell divided.

Genus, Chiton.—Shell constituting a series of imbricated dorsal plates.

The body is elliptical. The cloak is firm and cartilaginous, and variously marked on the margin. The dorsal plates are arched, and occupy the middle and sides of the back, where they are implanted in the cloak, in an imbricated manner, the posterior margin of the first valve covering the anterior of the second. The foot is narrow. The mouth is sur-

rounded with a semicircular curled membrane, and is destitute of tentacula. The anus consists of a short tube, placed at the posterior extremity of the cloak. The external orifice of generation has not been detected.

Genus, Chitonellus.—Dorsal plates not imbricated. In this genus, instituted by Lamarck (Hist. Nat. des Animaux sans Vertèbres, Vol. VI. p. 316), the shells are slender, narrow, and are disposed longitudinally, and not in contact, along the middle of the back, leaving the sides of the cloak naked. Two species, C. laevis and striatus, were brought from New Holland, by Peron and Le Sueur.

2. Body naked. Inferobranchia.

Genus, Phyllidia.—Anus placed dorsally near the extremity of the cloak.

M. Cuvier has given descriptions of three from the tropical seas, which differ remarkably in the protuberances of the cloak.

Genus, Diphyllidia.—Anus placed on the right side.

This genus was formed by M. Cuvier in his Regne Animal, Vol. III. p. 395, from an imperfectly investigated animal, in the cabinet of M. Brugmans at Leyden. The cloak is pointed behind, with a feeler and small tubercle on each side.

2. Tribe.

Branchiæ simple, and concealed when at rest under a lid. Tectibranchia of Cuvier.

A. Head furnished with tentacula.

1. Tentacula four in number.

a. Branchiæ lateral.

Genus, Aplysia.—Branchiæ with a corneous lid. The A. depilans, the type of the genus, is of frequent occurrence on the British shores. The A. punctata of Cuvier may be regarded merely as a variety.

It is probably at this place where the genus Gastroplox of Blainville, published by Lamarck, under the ill-judged title Umbrella (Hist. Nat. &c. Vol. VI. p. 339), should be introduced. The following is the extended character which he has communicated.

“Corpus valde crassum, obovatum, testa dorsali onustum; pede amplissimo, subtus plano, undique prominente, anterius sinu emarginato, postice attenuato. Caput non distinctum. Cavitatis infundibuliformis in sinu antico pedis os in fundo recondens. Tentacula quatuor: superiora duo, crassa, brevia, truncata, hinc fissa, intus transversim sublamellosa; altera duo, tenuia, cristata, pedicellata, ad oris latera. Branchiæ foliaceæ, serratim ordinatæ, infra cutis marginem per totam longitudinem lateris dextri. Anus post extremitatem posticam branchiarum.

“Testa externa, orbicularis, subirregularis, planulata, superne convexiuscula, albida, versus medium mucrone apicali brevissimo præbita; marginibus acutis: interna facie subconcava; disco calloso, colorato, ad centrum impresso, limbo levi cincto.”

Doubts seem to be entertained whether the shell is to be considered as belonging to the cloak or the foot. Two species are known.

Genus, Notarchus.—Lid of the branchiæ soft. There is an oblique groove from the neck leading to the branchiæ. The structure is similar to Aplysia. M. Cuvier instituted this genus in his Regne An. Vol. II. p. 395, and Vol. IV. Tab. xi. f. 1.

b. Branchiæ terminal.

Genus, Dolabella.—Dorsal plate a solid shell.

2. Tentacula two in number.

Genus, Pleurobranchus.—Cloak and foot expanded, between which, on the middle of the right side, the branchiæ are placed.

B. Head destitute of tentacula.

Genus, Bulla.—Body of the animal protected by a convoluted shell.

M. Lamarck is inclined to divide this genus into two, distinguishing those in which the shell is concealed, by the term Bullæa, from such as have the shell in part exposed, which he retains in the genus Bulla. The shells of the genus Bullæa are thin and white, as B. aperta; those of Bulla stronger, more opaque, and covered with an epidermis, which, after the death of the animal, is easily detached, as B. lignaria.

Genus, Doridium (of Mækel).—Destitute of a dorsal plate or shell.

There is a cavity in the cloak, with a spiral turn. The branchiæ, and accompanying organs, are placed far behind. There is here no appearance of a spinous tongue; the gullet is simple, and the stomach is membranaceous. D. carnosum, a native of the Mediterranean, is the type of the genus.

II. Order.

BRANCHIÆ INTERNAL.

These ærering organs are contained in a cavity, and appear in the form of sessile pectinated ridges.

1. Subdivision.

Heart entire, and detached from the rectum.

This group, forming the Pectinobranchia of Cuvier, includes nearly all the marine gasteropoda which have spiral univalve shells. It likewise contains a few species which inhabit the fresh water.

1. Tribe.

Shell external.

The shelly covering exhibits all the variations of the spiral form. The internal structure has hitherto been in a great measure neglected, so that the characters, employed in the methodical distribution of the species and genera, are derived from the shelly appendage of the cloak. The groups, therefore, are merely artificial temporary combinations.

A. Aperture of the shell entire.

As co-existent with this character of the shell, the anterior margin of the cloak, at the entrance to the branchial cavity, is found likewise to be entire.

1. Aperture of the shell closed by a pedal lid, or operculum.

The three following families appear to be the indications of as many natural groups, the genera of which admit of still more minute arrangement.

1. Family, Turbonidæ.—Aperture of the shell round or ovate. Mollusca.

This family includes the greater number of the species of the Linnean genus Turbo. The genera into which it is now divided may be distributed into two sections, from the residence of the animals.

1. Section, Marine.

The marine turbonidæ are of frequent occurrence, and compose the genera Turbo, Delphinula, Turritella, Scalaria, Odostomia, Monodonta, Phasianella, and Vermicularia. Some of the species are known to be ovoviviparous, and it is probable that the same kind of reproduction prevails in all of them. Remarkable differences may be observed in the form of the hood, the length of the peduncles supporting the eyes, and the number and distribution of the filaments surrounding the body.

2. Section, Fluviate.

The fluviate turbonidæ are limited in their number both in regard to genera and species. The genera are only three, Ampullaria, Melania, and Paludina. In the last of these, including the Helix vivipara and tentaculata, the sexes are distinct in different individuals.

2. Family, Neritidæ.—Aperture semicircular, with an oblique straight pillar-lip.

1. Section, Marine.

This includes the genera Nerita and Natica.

2. Section, Fluviate.

This contains only the genus Neritina, including Nerita fluvialis of Linnaeus.

3. Family, Trochusidæ.—Aperture of the shell subquadrate.

All the genera, including Trochus, Solarium, and Pyramidella, are marine. The cloak on each side is usually ornamented with three filaments.

2. Aperture of the shell exposed.—The foot destitute of a lid. Marine.

Genus, Janthina.—Foot with an adhering spongy body.

In this genus, represented by the Helix Janthina of Linnaeus, the spongy body is capable of changing its dimensions, and enabling the animal to sink or rise in the water at pleasure. When irritated, it ejects a purple fluid from the cellular margin of the cloak above the gills, not unlike the Aplysia.

Genus, Velutina.—Foot simple.

This genus was formed by us for the reception of the Bulla velutina of Muller (Zool. Dan. Tab. ci. f. 1, 2, 3, 4), the Helix laevigata of British writers.

B. Anterior margin of the aperture of the shell canalculated.

This groove in the aperture of the shell is produced by the anterior margin of the cloak being extended over the opening into the gills, for the purpose of acting like a tube or syphon, in conveying the water to and from the branchial cavity. The species are considered as oviparous, with distinct sexes in separate individuals.

1. Shell convoluted.—The shell has a lengthened

Mollusca. mouth parallel with its length. The whorls, which are small segments of large circles, are wrapped round the pillar, and rising little the one above the other, embrace or enclose the preceding ones. The four following families appear to belong to this division.

1. Family, Conusidæ.—Furnished with a long proboscis, and produced tentacula, with the eyes near the summit on the outside. The genera Conus and Terebellum form this family.

2. Family, Cypreadæ.—Cloak enlarged, and capable of folding over the shell. There is no lid. The genus Cyprea is the type.

3. Family, Ovuladæ.—Both extremities of the aperture canalculated. The inhabitants of all the genera, Ovula, Calpurnia, and Volva, are unknown. The last genus includes the Bulla patula of Pennant.

4. Family, Volutadæ.—Canal of the aperture abbreviated. Pillar-lip plaited. The foot appears to be destitute of a lid. The genera are numerous. Voluta, Oliva, Cymbium, Marginella, Cancellaria, Mitra, Ancilla, Volvaria, and Tornatella. The last genus contains the Voluta tornatilis of British writers.

2. Shell turritæ.—The whorls of the shell, the revolving spire of which is subconical, scarcely embrace one another, but are merely united at the margins. Three families may here be established.

1. Family, Buccinidæ.—Canal short, scarcely produced beyond the anterior margin of the lip, and bent towards the right. The tentacula are remote, and the head is destitute of a hood. The mouth has a retractile proboscis. The following genera belong to this family: Buccinum, Eburna, Dolium, Harpa, Nassa, Purpura, Cassis, Morio, and Terebra.

2. Family, Muricedæ.—Canal produced, and straight. The tentacula approach. The head and mouth as in the preceding family. The genera are, Murex, Typhis, Ranella, Fusus, Pleurotoma, Pyrrula, Fasciolaria, and Turbinella.

3. Family, Cerithiadæ.—Canal short and recurved. Head with a hood. This family contains the marine genus Cerithium, and the fluviatile one Potamidum.

4. Family, Strombusidæ.—Canal short, and bent towards the right. The outer margin of the aperture becomes palmated with age, and exhibits a second canal, generally near the former, for the passage of the head. The following are the genera: Strombus, Pterocera, and Rostellaria.

2. Tribe.

Shell internal.

This tribe consists at present of only one genus, termed Sigaretus, two species of which are natives of Britain.

2. Subdivision.

Heart traversed by the rectum.

This group includes the order Scutibranchia of Cuvier. In general form, and in structure and position of the branchiæ, the resemblance is very close to the genera of the preceding subdivision. They differ, however, in many particulars. The heart is furnished with two auricles, and is perforated by the intestine. The sexes appear to be incorporated in the same individual, or rather the male

organs are unknown. The body is protected by a shell, the aperture of which is wide, and never closed by a lid. Mollusca.

1. Tribe.

Shell ear-shaped, flat, with a lateral, and nearly concealed spire.

Family, Haliotidæ, including the genera Haliotis, Padola, and Stomatia. These genera exhibit well-marked characters in the shell. The left margin of the shell in Haliotis is pierced by a row of holes. In Padola, these holes are nearly obliterated; but there is an internal groove and external ridge in the line of their direction. In Stomatia, there are neither holes nor ridges.

2. Tribe.

Shell conical, simple, or slightly revolute at the apex.

A. Cavity of the shell interrupted by a testaceous plate. This division consists of three genera, each of which may be regarded as the type of a family, although, for the present, they all be included in one.

Family, Crepiduladæ.—The marine genera are, Crepidula and Calyptrea, the latter including the Patella Chinensis of British writers. There is only one fluviatile genus, termed Navicella.

B. Cavity of the shell entire.

1. Family, Capuladæ.—Shell entire.

This includes the genera Capulus (containing Patella Hungarica and antiquata of British writers) and Carinaria, represented by the Argonauta vitria.

2. Family, Fissurelladæ.—Shell with a slit, or perforation.

In the Fissurella, the apex of the shell is perforated. In Emarginula, there is a slit in the anterior margin.

II. DIVISION.

MOLLUSCA ACEPHALA.

Destitute of a distinct head or neck.

The animals of this division are much more simple in their organization than those of the preceding division. In none of the species are there any rudiments of organs of hearing or of sight. They are destitute of jaws or other hard parts about the mouth. They all inhabit the water, and possess branchiæ. The organs of the two sexes are incorporated in the same individual, and reciprocal union is unnecessary. They are either oviparous or ovoviviparous. The presence or absence of a shelly covering furnish characters for a twofold distribution of the groups.

I. Section.

ACEPHALA CONCHIFERA.

The shell, which in all cases is external, is bivalve, and exhibits very remarkable differences in the form

Mollusca. relative size, and connection of the valves. The cloak is likewise in the form of two leaves, corresponding with the valves which protect it.

I. Order.

BRACHIOPODA.

Mouth with a spiral arm on each side fringed with filaments.

The genera included in this group constitute the Brachiopoda of Cuvier. The lobes of the cloak are free anteriorly. From the body, between the lobes, the arms have their origin, at the margin of the mouth. These arms are capable of folding up spirally. All the species are permanently attached to foreign bodies, and inhabit the sea. Their nervous and reproductive systems have received but little elucidation.

1. Subdivision.

Shell supported on a fleshy peduncle.

Genus, Lingula.—Valves equal, the apex of both attached to the peduncle.

The peduncle is nearly cylindrical, cartilaginous, and covered with a membrane consisting of circular fibres. The valves are oval, flat, and destitute of teeth, or elastic ligaments. The adductor muscles are numerous, obliquely placed, and appear capable of giving to the valves a considerable degree of lateral motion. The cloak is thin, and has interspersed muscular fibres. Its margin is thickened, and fringed with fine hairs of nearly equal length.

The Lingula unguis is the only known species, the structure of which has been developed by Cuvier.

Genus, Terebratula.—Valves unequal, the peduncle passing through an aperture in the largest valve.

The arms are shorter than those of the Lingula, and are said to be forked. They are supported within by numerous arcuated plates.

M. Lamarck divides the recent kinds into two sections. 1. Shell smooth, or destitute of longitudinal ribs. The T. cranium, a native of the Zetland seas, may be quoted as an example. The peduncle is simple. 2. Shell ribbed longitudinally. The T. aurita, which inhabits Loch Broom, is another, though recently discovered, British example. The larger valve is broadest in the middle, semicircular in front, and narrowing towards the apex, in consequence of the sides being compressed or bent inwards. The ribs from the beak towards the anterior margin are the most distinct, rounded, and about eight in number; those towards the sides are obsolete. The under valve is nearly orbicular, with the margin at the hinge truncated, or rather obtusely angular, and having the sides depressed, and forming small auricles, as in the genus Pecten, but not produced. The ribs are obsoletely wrinkled across, and the margin is waved by the ribs being concave internally. The inner surface of both valves, especially the largest, is finely punctulated. The hinge is formed by a projection on each side, the proximal margin of the perforation in the large valve entering corresponding depressions in the smaller one. The margin of the perforation itself is completed by the application of the smaller valve. The peduncle is short, and consists of numerous un-

Mollusca. equal-sized tubular threads, attached by a complicated tendino-muscular apparatus, chiefly to the larger valve. The spiral arms seemed to have simple summits, and to be destitute of testaceous plates. The smallness and probable youth of the subject, however, rendered minute examination of the structure impracticable. Trawled up in Loch Broom, near the harbour of Stornoway, 16th August 1821. This species approaches nearest to the T. truncata.

The fossil species of this genus are numerous, and occur in the older and newer of the floetz formations. They furnish obvious characters for the construction of many genera, some of which have been already established.

2. Subdivision.

Shell sessile.

Genus, Criopus.—Under valve cemented to stones.

The under valve is membranaceous, flat, and adhering; the upper is flatly conical, and resembles a patella, in which genus, from neglecting the structure of the animal, it has usually been placed.

The C. anomalus, Patella anomala of Muller, Zool. Dan. Tab. v. f. 1, 8, has a branched double ovary, with round eggs. It has been described and figured as a native of the Zetland seas, under the term Patella distorta, in Edin. Encyclopædia, Vol. VII. p. 65, Tab. cciv. f. 4; and Lin. Trans. Vol. XI. p. 195, Tab. xiii. f. 5.

II. Order.

BIVALVIA.

Mouth destitute of fringed spiral arms.

The animals of this group form the class Coachi-fera of Lamarck, the Bivalvia of the older naturalists.

The shells exhibit great variety of form and relative size. They are joined together at the hinge, which is either plain or toothed, and corresponds in position with the back of the animal. The connection of the two valves is secured by the intervention of an elastic horny ligament, the office of which is to keep the valves open. It is either external or internal. The valves are closed by means of adductor muscles, intermixed with tendons, and, passing transversely through the animal, adhere to the corresponding places in the inside of each shell. By the contractions of these muscles the free edges of the valves are brought into contact, at the same time that the ligament is compressed or stretched, according as it is internal or external. The number of muscular impressions is employed by Lamarck in the division of the Bivalvia into two orders, Dimyaires and Monomyaires. This distinction, however, he has not attended to with care, as in his family Mytilacées, which he includes in his second order, or those having one adductor muscle, there are obviously two adductor muscles, although the one is certainly much larger and more complicated than the other. Besides these impressions of the adductor muscles, there are others connected with the foot and byssus. The cloak lines the inside of the shells. In some cases it is entirely open, when the border corresponding with the free margin of the shell is thickened, and more or less fringed with contractile irritable filaments. In other cases the cloak in front is more or less united, and

Mollusca. even forms tubular elongations, which are termed syphons.

Locomotion is denied to many species of this order. Among these some are immovably cemented to rocks and stones, as oysters; a few are attached by a cartilaginous ligament, as the Anomia; while others are fixed by means of a byssus. This last organ consists of numerous filaments issuing from a complicated apparatus in the breast, connected with a secreting gland and with the shell by the intervention of tendinous bands. The foot is seated a little towards the mouth, is usually tongue-shaped, capable of considerable elongation, with a furrow on its posterior surface. This organ, where a byssus is present, is considered as employed in opening and fixing the threads. When there is no byssus, it either acts as a sucker, enabling the animal to crawl among the surface of bodies, or as a paw, to dig holes in the sand or mud. None of the species can float in the water. They either crawl or leap, the last kind of motion being effected by suddenly opening and shutting the valves. In securing a residence, some of the species bore into different substances by means of a rotatory motion of the shell. It was at one time supposed that the dwelling was formed by a secretion affecting the solution of the surrounding substance. But the very different substances penetrated by the same species, as limestone, slate-clay, and wood, forbid us to entertain such a supposition.

The nervous system is here but little developed. The superior and inferior ganglia, surrounding the gullet, give rise to all the nervous filaments which proceed through the body.

The digestive organs are scarcely less simple. The food is soft and swallowed entire, and either brought to the mouth by accident, or by eddies produced in the water, by the opening and shutting of the shells, aided in some cases by the syphons.

It may be proper here to state, in order to understand the relative situation of the parts, that, upon laying the animal upon its back, and opening the cloak, the abdomen appears to occupy the middle longitudinally, and the branchia to be arranged on each side. The mouth is situated at the anterior extremity, and consists of a simple aperture entering into the gullet, or rather stomach. It is surrounded by four flattened moveable tentacula, two of which in some are in part united with the cloak, while in others they are free to the base. In their structure they resemble the branchia. The stomach is full of cells, the bottom of each pierced with a biliary duct. A singular organ, termed the crystalline process, cylindrical, cartilaginous, and transparent, is found in some species projecting into the cavity of the stomach. The liver is large, surrounds the stomach, and pours out its contents by numerous openings. The intestine terminates posteriorly by a tubular anus.

The branchia consist of two ribbands on each side, extending the length of the body, free on the sides and margin, and striated transversely. These plates are frequently of unequal size. The blood is brought to these by means of pulmonic veins, without the intervention of the heart. The aerated blood is transmitted to a systemic heart, consisting of one or two auricles, and a ventricle.

The reproductive organs of the Bivalvia, hitherto

examined, consist of an ovary occupying the sides of the body, and penetrating the membranes of the cloak. They appear to have the organs of both sexes incorporated, and to propagate without intercourse. Lamarck is disposed to consider impregnation produced by the male fluid dispersed through the water; a supposition unsupported even by analogy in the animal kingdom. Many species are ovoviviparous; in which case the eggs when ripe pass into the gills, where they are hatched.

The methodical distribution of the Bivalvia appears to be attended with peculiar difficulties, in consequence of the uniformity which prevails in the structure and disposition of their organs. The characters furnished by the shell, though useful in the construction of generic as well as specific distinctions, have been abandoned by those who prefer a knowledge of the structure, rather than the form of an animal. The characters derived from the presence of a byssus, a foot, or syphons, appear to be nearly of co-ordinate importance. M. Cuvier gives the preference to those founded on the appearances of the latter, and distributes the genera into five families, an arrangement which we here propose to follow. These, however, may be considered as occupying a much higher rank, and each as including numerous families.

1. Subdivision.

Cloak open.

There are no syphons, the anterior margin of the cloak being as open as the mouth of the shell. When the valves open, the water comes immediately in contact with the branchia and mouth. The margin of the mantle has a double fringe of filaments.

1. Tribe.

Valves closed by one adductor muscle.

A. Pectenidæ. Animals free or fixed only by a byssus. Furnished with a foot.

Into this family, contemplated by Lamarck, the following ill assorted genera may be placed: Pecten, Lima, Pedum, Plicatula, Vulsella, Placuna, Gryphaea, Perna, and Crenatula.

B. Ostreaæ. Shell cemented to foreign bodies. Body destitute of a foot.

To this family the following genera are related: Ostrea, Spondylus, and Anomia. The last genus ought to form a family apart.

2. Tribe.

Shell closed by two adductor muscles.

The two genera, Avicula and Meleagrina (of Lamarck), form one family of this tribe; the genus Pinna another; and the Arcadæ a third, including Arca, Pectunculus, Nucula, Cucullæa, Trigonia, and Castalia.

2. Subdivision.

Cloak more or less closed, forming syphons.

The further division of this group depends on the modifications of the syphons, or aperture of the cloak.

1. Tribe.

The union of the cloak forming only one syphon. This is situate posteriorly opposite the anus, and serves for the purpose of the excrements. The other

Mollusca. large opening allows the water to enter to the mouth and gills.

This tribe may be divided into two families. The first, Mytilusidæ, will include the genera Mytilus, Modiolus, and Lithodomus, which are furnished with a byssus. The second, Uniodæ, will embrace Unio, Ilyria, Anodonta, and Iridina. They want a byssus.

M. Cuvier is disposed to place in this group the genera Cardita, Venericardia, and Crassatella.

2. Tribe.

Cloak closed posteriorly, and anteriorly forming three apertures. The first serves for the passage of the byssus, and is the largest. The second admits water to the branchiæ and mouth; and the third is opposite the anus. The valves are closed by one adductor muscle. There are only two genera belonging to this tribe, Tridacna and Hippopus.

In the two remaining tribes there are three openings in the cloak. Two of these are posterior, and near each other; sometimes, indeed, they are tubular and united. There is no byssus, but always a foot.

3. Tribe.

Anterior opening large, allowing the water free access to the mouth and gills, and the feet freedom of motion. The structure of the animals is yet too imperfectly examined, to enable any one to establish families on permanent characters. The attempt which Lamarck has made may be considered as a complete failure, independent of the wanton changes of nomenclature with which it is chargeable. The following are the principal genera belonging to this tribe: Chama, Isocardia, Cardium, Donax, Cyclas, Corbis, Tellina, Loripes, Lucina, Venus, Capsa, Petricola, Corbula, and Mactra.

4. Tribe.

Anterior opening small, and not exposing the mouth or gills.

In this tribe the mantle is closed in front; and even when the valves are open, neither mouth nor gills are visible. The anterior opening serves for a passage to the foot, and the posterior openings, in the form of two long tubes, united by a common membrane, serve for the entrance and exit of the water to the mouth and branchiæ, and the ejection of the feces, the dorsal syphon serving the latter purpose. The cuticle of the shell covers also the exposed portion of the cloak, so that, when the animal is removed from the shell, it remains as a loose membrane on the margin of the valves, as was first observed by Reaumur. All the genera prefer concealment, burrowing in sand, mud, or wood, with the head downwards, and the syphons rising to the surface. The following genera belong to this tribe: Mya, Lutrina, Anatina, Glycimeris, Panopea, Pandora, Gastrochena, Byssomia, Hiatella, Solen, Sanguinolaria, Pholas, Teredo, and Fistularia.

II. Section.

ACEPHALA TUNICATA.

Covering soft or coriaceous:

The formation of this interesting group of animals

was first publicly announced by Lamarck in his Histoire Naturelle des Animaux sans Vertèbres, Tom. III. p. 80 (1816). The labours of Desmarest, Lesueur, and Cuvier, aided by the descriptions of Ellis and Pallas, paved the way for the masterly efforts of Savigny, to whom we owe the most extensive, now, and accurate information yet given concerning the animals of this group. His observations are contained in his Recherches Anatomiques sur les Ascidies composées, et sur les Ascidies simples, inserted in his Mémoires sur les Animaux sans Vertèbres. 8vo. Paris, 1816.

The covering of the animals of this group consists of an external and internal sac or tunic, which are either entirely united or unconnected, except at the apertures. The surface is smooth in some, and rough in others, and in a few species defended by an artificial covering of agglutinated shells and sand. The sacs are furnished with muscular bands, and are capable of contraction. Some of the species, by means of contractile movements, float about in the water; others, receiving that element into the branchial cavity, and ejecting it forcibly at the opposite one, push themselves forward. Many, however, are fixed during life to seaweeds and stones.

The apertures of the tunic are two in number, unless in the doubtful genus Mammaria. The one, frequently the largest, is destined for receiving the water into the cavity to supply the mouth and gills. This is termed the branchial cavity. The other is destined for the exit of the water, the eggs, and the feces, and termed the anal opening. These apertures are sometimes placed near each other, at other times at opposite extremities of the body, and variously provided with tentacula or valves.

The mouth is simple, destitute of spiral arms, and opening in the interior of the cavity of the body between the branchiæ, as in the other Acephala. It possesses neither jaws nor tentacula. The alimentary canal is very simple, and can scarcely be distinguished into gullet, stomach, and intestine. The food is soft, and such as the bounty of the waves bestows. The liver adheres to the stomach, and in many species is divided into distinct lobes.

The circulating system appears to be reduced to a single systemic ventricle. The gills cover the walls of the cavity, in the form of ridges, more or less complicated, and seldom symmetrical.

The reproductive organs consist of an ovarium, either simple or complicated, with some additional glands, the uses of which have not been ascertained. They are considered as hermaphrodite, and independent of reciprocal impregnation. They appear not only to be oviparous, but to be gemiparous and compound, many individuals being organically connected, and capable of simultaneous movements. They are all inhabitants of the sea.

1. Subdivision.

Interior tunic detached from the external one, and united only at the two orifices.

The branchiæ are large, equal, and spread on the central walls of the inner sac. The branchial orifice has an inner membranaceous denticulated ring, or a circle of tentacula.

Body permanently fixed to other bodies.

In this tribe the branchial and anal orifices are not opposite each other, and do not communicate through the branchial cavity. This cavity at its opening is furnished with tentacular filaments. The branchiae are conjoined anteriorly.

A. Simple.

This division includes the genus Ascidia of Linnaeus. The individuals are independent of each other, and although they frequently adhere together in clusters, they are destitute of a common covering, or organical connection.

1. Apertures furnished with four rays.

The animals of this group have the external tunic coriaceous, dry, opaque, rough, folded, and frequently covered with extraneous bodies, or inclosing such. The branchial orifice has four rays, the anal one the same, or divided transversely. The branchiae are divided longitudinally into persistent regular deep folds.

a. Body pedunculated.

The peduncle, in this division, may be said to have its rise in the summit of the body, which it serves to suspend. The abdomen is lateral. The meshes of the branchiae are destitute of papillae.

Genus, Boltenia.—The tentacular filaments of the branchial circle are compound. There is no liver, and the ovarium is compound. Only one species is known, B. fusiforme. Savigny, Mem. Tab. i. f. 1. and Tab. v. f. 5. It is the Vorticella Bolteni of Linnaeus and the Ascidia clavata of Shaw.

b. Body sessile.

M. Savigny describes this group as a genus, which he terms Cynthia, which he divides into four subgenera.

(A.) Tentacular filaments of the branchial orifice compound. The folds of the branchiae more than eight in number. The liver distinct, and surrounding the stomach. Ovarium divided, with one division at least on each side the body. The intestine destitute of a rib.

Genus, Cynthia.—Meshes of the branchiae unchanged by the folds. C. Momus. Sav. Tab. i. f. 2.

Genus, Cesira.—Meshes of the branchiae interrupted by the folds. C. Diona of Sav. Tab. vii. f. 1. The Ascidia quadridentata of Forskål.

(B.) Tentacular filaments of the branchial orifice simple. The folds of the branchiae eight in number, four on each side, and the meshes uninterrupted. Intestine strengthened by a cylindrical rib from the pylorus to the anus. Liver absent or indistinct.

Genus, Styela.—Ovarium divided, one division at least on each side. S. Canopus. Sav. Tab. viii. f. 1.

Genus, Pandocia.—Ovarium single, and situate in the fold of the intestine. The Ascidia conchilega, a native species, is the type.

2. Apertures with indistinct rays, or more than four.

The external tunic is here soft, easily cut, and translucent. The rays (when existing) of the branchial orifice amount to eight or nine; and those of the anal to six at least. The branchiae are destitute

of longitudinal folds. The tentacular filaments of the branchial circle are simple. Liver indistinct. Ovarium single. Mollusca.

a. Body pedunculated.

The stalk is here placed at the base, and serves to support the body, being of an opposite character from that of the Boltenia.

Genus, Clavelina.—Branchial and anal orifices without rays. Angles of the branchial meshes simple. Intestine destitute of a rib. The Ascidia clavata of Pallas, and the A. lepadiformis of Muller, belong to this genus; the latter of these is now recorded as a British species.

b. Body sessile.

The branchial orifice with eight or nine rays, and the anal with six. The angles of the branchial meshes with papillae. No liver. A cylindrical rib extending from the pylorus to the anus.

(A.) Tunic and branchial cavity straight.

Genus, Pirena.—The branchial sac as extended as the tunic. Stomach not resting on the intestine. P. phusca of Forskål is the type, to which Savigny has added three other species. The Ascidia prunum of Muller, a native species, is probably of this genus.

Genus, Ciona.—Branchial sac shorter than the tunic, and exceeded by the viscera. C. Ascidia intestinalis, Lin. is a native example of this genus.

(B.) Tunic turned up at the base.

Genus, Phallusia.—Branchial sac extending beyond the viscera into the pouch of the sac. Stomach resting on the mass of viscera. The Ascidia mentula of Muller, a native species, is the type.

There are two genera supposed to be nearly related to the preceding, which are involved in great obscurity. The genus Bipapilaria of Lamarek appears to be pedunculated, with two apertures, each furnished with three setaceous tentacula. The Mammaria of Muller has only one terminal aperture. One species inhabits the British seas.

B. Compound.

The animals included under this division were formerly included in the genus Aleçonium of Linnaeus, and placed among the Zoophytes. They are compound animals, many individuals united by a common integument, and arranged according to a uniform plan.

In some cases, there is only one system of individuals in the mass, in other cases, there are many, similarly arranged and contiguous. The tentacular filaments of the branchiae appear to be distinct. They are destitute of the intestinal rib which occurs in some of the preceding genera.

1. Branchial Orifice Radiated.

a. Branchial and anal orifices, with six rays.

(A.) Body sessile. The angles of the branchial meshes furnished with papillae. The thorax, or cavity containing the branchiae, cylindrical. The abdomen is inferior, with a stalk. Ovarium sessile, and single.

Genus, Diazona.—Body orbicular, with a single system of animals disposed in concentric circles.

The substance is gelatinous. The ovarium en-

Mollusca. closed in the fold of the intestine. D. violacea of Sav. Tab. ii. f. 3.

Genus, Polyzona.—Body polymorphous, with many systems disposed subcirculary.

The body is subcartilaginous. The individuals are disposed irregularly around the common centre. Savigny inadvertently termed this genus Distoma, a name long precopied among the Intestina. The Alcyonium rubrum of Plancus, and the Distomus variolosus of Gaertner, belong to this genus. The last is a native species.

(B.) Body pedunculated.

Genus, Sigillina.—Body a solid cone, consisting of a single system of many individuals, irregularly disposed, one above the other.

The thorax is short, and hemispherical. The angles of the branchial meshes destitute of papillæ. The abdomen is inferior, sessile, and larger than the thorax. The single ovary is pedunculated. S. australis, Sav. Tab. iii. f. 2. brought from New Holland, by M. Peron, is the only known species.

b. Branchial orifice only furnished with six rays.

(A.) Body pedunculated. System single, circular, and terminal.

Genus, Synocum.—Anal orifice rayed.

The body is cylindrical. The anal orifice has six very unequal rays; the three largest forming the exterior margin of the central star. The stomach is simple. The angles of the branchial meshes destitute of papillæ. Ovary single, sessile attached to the bottom of the abdomen, and descending perpendicularly. The S. turgens of Phipps is the type. In the month of August 1817, we observed at the Isle of May another species, adhering to a rock, and differing from the turgens chiefly in the smoothness of its skin.

Genus, Sydneyum.—Anal orifice simple and tubular.

The body is inversely conical. The stomach surrounded with glands. Intestine spirally folded. Ovary pedunculated. The S. turbinatum is the only known species, and was sent to Savigny by Leach from the British seas.

(B.) Body sessile, polymorphous.

(a.) Each system with a central cavity.

Genus, Polyclinum.—Systems numerous, convex stellular. Individuals arranged irregularly round the common centre. Abdomen inferior pedunculated, and less than the thorax. Ovary single, pedunculated, and attached to the side of the abdominal cavity, and drooping.

M. Savigny describes one species from the Mauritius, and five from the Gulf of Suez.

(b.) Systems destitute of central cavity, and the angles of the branchial meshes without papillæ.

Genus, Alpidium.—Individuals in a single row round the common centre.

The thorax is cylindrical. The abdomen inferior sessile, and of the size of the thorax. Ovary single, sessile, placed at the bottom of the abdomen, and prolonged perpendicularly. Savigny divides the genus into two tribes. In the first, the individuals are simply oblong, with an ovary shorter than the body, as A. ficus (Alcyonium ficus, Linn.). In the

Mollusca. second, the individuals are filiform, with an ovary longer than the body, as A. effusum of Savigny, Tab. xvi. f. 3.

Genus, Didemnum.—Individuals in indistinct systems.

The thorax is short and subglobular. The abdomen inferior, pedunculated, and larger than the thorax. The anal opening is obscure. The ovary is single, sessile, and placed on the side of the abdomen. D. candidum and viscosum, from the Gulf of Suez, are the only known species.

2. Branchial Orifice simple.

The species form a thin fleshy crust on stones and sea-weeds. The individuals are stellularly arranged in distinct systems. The branchial orifice is circular and undivided. The abdomen is sublateral, and fixed at the bottom of the branchial cavity. The intestine is small, and the anus indistinct. The angles of the branchial meshes are without papillæ.

Genus, Botryllus.—Systems furnished with a central cavity.

The systems are prominent, and consist of one or more regular concentric rows. The ovary is double, being attached to each side of the branchial sac.

This genus is subdivided by Savigny into Botrylli stellati, and Botrylli conglomerati. In the first, where the individuals are distributed in a single row, there are some species in which the individuals are cylindrical with approaching orifices, and the limb of the central cavity not apparent after death and probably short, as the B. rosaceus Leachii and Borlasii. In other species, the individuals are ovoid, with remote orifices, and the limb of the central cavity is always apparent and notched, as B. Schlosseri, stellatus, genmerus, and minutus. In the Botrylli conglomerati, in which the individuals are disposed in several rows, there is only one species, B. conglomeratus.

Genus, Eucelium.—Systems destitute of a central cavity.

The individuals are distributed in a single row, and the ovary is single, sessile, and attached to the side of the abdominal cavity. The E. hospitolum of Sav. Tab. iv. f. 4, is the only known species.

2. Tribe.

Body free, and moving about in the water.

Genus, Pyrosoma.

The body is gelatinous, in the form of a lengthened bag open at the widest end. The individuals are arranged perpendicularly to the axis of the central cavity, super-imposed on one another. The branchial orifice is external, without rays, and with an appendage over its upper margin. The anal orifice is opposite, and terminates in the central cavity. Branchial sac destitute of folds, with a membranaceous ring at the entry. The branchiæ are disjoined. The abdomen is inferior to the branchiæ, and not separated by any contraction. Liver distinct, globular, and retained in a fold of the intestine. Ovary double, opposite, and situate at the upper extremity of the branchial cavity.

M. Savigny divides the species into Pyrosomata

Mollusca. verticilla, having the individuals arranged in regular prominent rings, as P. elegans of Lesueur; and Pyrosomata paniculata, having the individuals forming irregular circles unequally prominent, as P. giganteum and Atlanticum.

2. Subdivision.

Inner tunic adhering throughout to the external one.

The body is gelatinous, transparent, and simple. The branchial cavity is open at both ends, communicating freely with the anus. The branchial orifice is in the form of a transverse slit, with one edge in the form of a valve, to accelerate the entrance of the water into the cavity. The inner tunic is strengthened by numerous transverse muscular bands, which, by contracting, diminish the diameter of the cavity, and eject the water from the anal orifice, thereby propelling the body through the water. The digestive organs are situate at the inner end of the cavity. The mouth and rectum are simple; the former placed between the two branchiæ, the latter directed towards the anal orifice. The heart is contiguous to the stomach, at the bottom of what may be termed the branchial sac, and is enveloped in a membranaceous pericardium. The branchiæ are double, not incorporated with the walls of the sac, but with two folds of unequal length. The largest is free in the middle, fixed at each extremity, and opposed to the dorsal groove, and traverses the cavity obliquely. The other extends from the base of the first to the extremity of the dorsal groove. The surface of the branchiæ consists of transverse vessels in a single range in some species, and a double range in others. When young, many individuals often adhere, and

form chains and circles. But the fully grown individuals are always detached and single.

This subdivision comprehends the species of the genus Salpa; they are exceedingly numerous, and appear to belong to many different genera. M. Cuvier has given indications of some of these, chiefly derived from the shape. A few are furnished with an elevated crest or fin, as the Thalia of Brown; a few have both extremities rounded or truncated, as Salpa octofera of Cuvier; others have one extremity produced, as Holothuria zonaria of Gmelin; and even both extremities produced, as Salpa maxima of Forskael. The Salpa moniliformis, so common in the Hebrides, and first recorded as a native by Dr Macculloch, in his valuable Description of the Western Isles, Vol. II. p. 188, and imperfectly figured in its young state, at Tab. xxix. fig. 2, appears to be closely allied to the S. maxima of Forskael, and but very remotely with the S. polycratica and confederata with which it is compared. This observer states, that "It cannot bear to be confined in a limited portion of water, as it died even in a ship's bucket in less than half an hour." With us, in similar circumstances, those taken in the evening were alive at noon on the following day.

The preparation of molluscous animals for exhibition in a museum is attended with peculiar difficulty. The shells, indeed, need only to be cleaned with a soft brush, and the marine kinds to be steeped in fresh water to extract all the saline ingredients, and dried, when they are fit for the cabinet. The soft parts, however, can seldom be distended by any substance, and dried. They are usually, therefore, preserved in spirits of wine, where but too frequently they appear a shapeless mass. (q. q.)

TABLE

OF THE

ARTICLES AND TREATISES

CONTAINED IN THIS VOLUME.

HUNTINGDONSHIRE.

HYDRAULICS.

IMPROVISATORI. (See ITALY.)

INGENHOUSZ (JOHN).

INVERNESS-SHIRE.

IONIAN ISLANDS.

IRON-MAKING.

JURISPRUDENCE.

JUSSIEU (ANTOINE DE).

— (BERNARD DE).

KALEIDOSCOPE.

KANT (IMMANUEL).

KENTUCKY. (See UNITED STATES.)

KERGUELEN'S LAND.

KILKENNY.

KINCARDINESHIRE.

KING'S COUNTY.

KINROSS-SHIRE.

KIRKCUDBRIGHTSHIRE.

KLINOMETER.

KOOKIES, OR LUNCTAS.

LACCADIVES.

LAGRANGE (JOSEPH LEWIS).

LALANDE (J. J. DE).

LAMBERT (JOHN HENRY).

LAMPS.

LANARKSHIRE.

LANCASHIRE.

LANGUAGES.

LEICESTERSHIRE.

LEITRIM.

LEMONNIER (PETER C. C.)

LEWIS.

LEYDEN (JOHN).

LIBERTY OF THE PRESS.

LIFE PRESERVERS. (See PRESERVERS.)

LIMERICK.

LINCOLNSHIRE.

LINLITHGOWSHIRE.

LITHOGRAPHY.

LONDON.

ERRATA.

VOLUME FOURTH.

Page 470, col. 2, line 55, for "Unterthaner," read "Unterthanen."
— 513, col. 1, line 25, for "Almadon," read "Almaden."
— 519, col. 2, line 27, for "Ocasia," read "Ocana."
— 520, col. 1, line 51, for "Astrato," read "Atrato."
— 521, col. 2, line 29, for "Agent," read "Agents."
— line 38, for "Velen," read "Velez."
— 523, col. 1, line 26, for "Carthage," read "Carthago."
— 524, col. 1, line 46, for "Pichinca," read "Pichincha."
— 525, col. 1, line 35, for "Meguil," read "Miguel."
— 526, col. 1, line 57, for "Bracameros," read "Brancamoros."
— 530, col. 1, line 15, for "Mompox," read "Mompox."
— 533, col. 1, line 55, for "Ortin," read "Ortiz."
— 600, col. 1, line 37, for "Tobasco," read "Tabasco." Lower in the same page the same correction.
— 601, col. 1, line 38, for "after furnishing abundance to the 30,000," read "after abundance to the inhabitants amounted to 30,000."
— 604, col. 1, line 18, for "Oyapoe," read "Oyapoc."
— 619, col. 1, line 6 from the table, for "Ubzen," read "Uelzen."
— 622, col. 1, line 56, for "none of whom," read "most of whom."
— col. 2, line 45, for "Leipsigen," read "Leipsiger." The same occurs twice more in the same page.
— 623, col. 2, line 58, for "Eimen," read "Eimer."

VOLUME FIFTH.

DISSERTATION FIRST, PART SECOND.

Page 24, line 10, for "νῆρα," read "νῆρα."
— 28, line 21, for "ce," read "ce."
— 45, line 12, for "ἄριστος," read "ἄριστος."
— 69, line 23, for "te," read "le."
— 89, line 26, for "sons," read "son."
— 156, line 24, for "ce," read "ce."
— 223, line 21, for "puisq' ainsi," read "puisqu' ainsi."
— 226, line 17, for "regence," read "regence."
— 240, line 32, for "philosophie," read "philosophie."
— 245, line 25, for "philosophie," read "philosophie."
Page 81, col. 2, line 5, for "standings," read "landings."
— 84, col. 2, in the wood cut, the lower B ought to be C.
— 86, col. 1, line 6, for "Geneva," read "Genoa."
— 128, for "Tybur," read "Tiber."
— 258, col. 1, line 16, insert "twice" at the beginning of the line, and read "violations" for "violation."
— 259, col. 1, line 30, for "interpretation," read "imputation."
— 259, col. 2, line 40, for "legislature," read "legislative."
— 262, col. 2, line 37, for "case," read "cure."
— 265, col. 2, line 4 from the bottom, for "consequences," read "consequence."
— 266, col. 2, line 17 from the bottom, for "verbally," read "virtually."
— 267, col. 1, line 12 from the bottom, for "l'impurité," read "l'impunité."
— 269, col. 1, line 21, for "exact," read "excite."

DIRECTIONS

DIRECTIONS FOR PLACING THE PLATES.

* * The Binder will observe, that the two concluding pages of METEOROLOGY, marked with Asterisks, are not to be cancelled.