I. LIMAN. Slug.—The body is lengthened, and some what pointed behind. The cloak is corrugated, and supports the shield on the forepart of the hack towards the head, containing a thin corncous or testacenus plate. The pulmonary cavity opens on the right side, at the inferior margin of the shield. Behind this opening is the anus. The sexual opening is underneath the su perior tentaculum, on the right side. At the termination of the body, above, is an opening, out of which a thick glutinous fluid oozes. The surface of the whole body is liberally supplied with a glutinous secretion of the same sort, but thinner in its consistence. This fluid issues from the pores of the skin and the pulmonary cavity, and when the animal is placed before the fire, it is given out in considerable quantities. The respectable editors of the Journal d' Histoire Nature/le, vol. i. p. 477, recom mended a lute made of this fluid, reduced to a proper consistence by quicklime, fur the purpose of securing the mouths of the bottles containing anatomical prepara tions, and preventing the evaporation of the alcohol. With this cutaneous secretion some of the species are capable of forming a thread, by which they are able to suspend themselves from the branches of trees. This mode of assisting locomotion is recorded by Lister, (ilninzalitn Anglia, p. 130.) and subsequently noticed by other observers. Linn. Trans. vol. i. p. 182 ; and vol. iv. p. 85.
The mouth consists of lips, which are capable of small extension, and above, the entrance is armed with a concave corneous jaw, with a notch in the middle. The tongue is merely armed with soft transverse ridges, pointed before, and terminated by a short cartilaginous cone. There is a sensible dilatation of the gullet, which marks the place of the stomach, at the under extremity of which is the rudiment of a ct.ecuin at the pyloric operting. The intestine makes several folds, chiefly in the liver, before it reaches the anus. The salivary glands reach to the extremity of the gullet. The liver is di vided into five lobes, which gives rise to two ducts that open into the pylorus.
The circulating system consists of two ven? cavx, which give out numerous branches to the pulmonary cavity. The aerated blood is conveyed by several ducts to a simple membranaceous systemic auricle. Be tween the auricle and ventricle there are are two valves. The ventricle is more muscular than the auricle. The arteries, which take their rise from a single aorta, arc characterised by a peculiar opacity and whiteness of co lour, as if they were filled with milk.
The organ of viscosity, nearly encircles the pericar dium. It consists of regularly pictinated plates. Its excretory canal terminates at the pulmonary cavity.
The organs of generation consist, in the female parts, of an ovarium, oviduct, and uterus ; and in the male, of a testicle, vas deferens, and penis, together with the pe duneulated vesicle; and, us common to both the sexual organs, there is a cavity opening externally, in which, by separate orifices, the uterus, penis, and vesicle ter minate.
The species of this genus have hitherto been chiefly characterised by the shape and colours of the body ; the latter, however, is liable to such great variation, that it is difficult to determine the number of species which are natives of The structure of the shield, and the relative position of the pulmonary cavity, joined with the markings of the body, ought to be resorted to ; and could a knowledge of the internal structure he likewise obtained, we might then hope to be able to bestow on the species permanent marks of distinction.
Although the terrestrial gasteropoda may be consi dered as phytivotous, it is now known that the larger species of this genus likewise feed on the common earth worm, as has been observed by Mr. Power, (Linn.
Trans, vol. ix. p. 323.) None of these species are used in this country as food.
II. PARMACELLA.—The animals of this genus are distinguished by the position of the shield, which is placed on the back, near the middle of the body, and contains, at its caudal extremity, an open subspiral tes taceous plate. Underneath the shield is the pulmonary cavity.
The only species of this genus yet known was found by M. Olivier in Mesopotamia. The genus was insti tuted by M. Cuvier, and the species denominated P. olivieri. Along the back, from the shield to the head, are three grooves ; the medial one is double. From the dissections of Cuvier, it appears that the internal struc ture of this species bears a close resemblance to that of the slugs. The most remarkable difference is in the two conical appendages of the common sexual cavity, by which they approach the Helices.
III. TESTACELLA.—The shield in this genus is placed on the posterior extremity of the body, and consequently the anus and pulmonary cavity are nearly terminal. These are protected by an open subspiral testaceous plate. The foot extends on each side beyond the body. From the manner in which the blood is aerated, the auri cle and ventricle are placed longitudinally, the latter being anterior.
The T. haleotoidca, described and figured in the His Loire Xaturelle des Mollusques Terrestres a Fluviatiles de to France, par M. Draparnaud, p. 121. tab. xi. figs. 12-14, is the only species which has been distinctly as certained. It lives in the soil, and pursues and feeds on the common earthworm.