LIMA X. 



47 



ment of the body to all the others ; and in certain 

 situations where the pround is ill adapted to the 

 animal's locomotion, a slimy juice is expelled from its 

 body to smooth the path, or give an additional hold 

 to its footing. The skin of the slug is very thick, but 

 more particularly at the anterior part ot the back, 

 where it forms a sort of fleshy fold or shield, extend- 

 ing more or less over the sides of the animal's body ; 

 in the interior of this is contained a rudiment of shell 

 in the shape of a small detached flat osseous sub- 

 stance in some species, and in others there are only 

 corpuscular grains or elementary parts of bone to be 

 discovered ; these are not exhibited on the exterior, 

 but doubtless tend to guard the pulmonary cavity 

 which lies on the right side immediately beneath this 

 shield or fleshy cowl. The animal has four teritacula, 

 retractile, and capable of considerable extension ; the 

 larger or posterior pair are furnished with eyes at 

 their summits ; these, with the other tentacula, assist 

 as feelers to avoid danger, and are probably furnished 

 with organs of smell to guide the animal to its food, 

 its visual faculties appearing extremely limited. These 

 tentacula constitute an important part of the animal's 

 economy of structure, so much so indeed that nature 

 is said to renew them when they have been destroyed 

 by accident or philosophical cruelty ; the fact does 

 not, however, rest upon any confirmation of our own, 

 though it is corroborated by analogous circumstances 

 in other molluscous animals, which leave but little 

 doubt of its truth. Abundant as these molluscs are, 

 they are difficult to separate into species, and only a 

 few appear to have been distinctly characterised by 

 naturalists; their habitat is also equally general, as 

 they are found in the tropical and northern hemi- 

 spheres, where, like the snail, they perform the func- 

 tions of their existence with greater advantage to 

 mankind than they receive credit for. Had our limits 

 permitted, we should have been pleased to have had 

 an opportunity of carrying on this article to a some- 

 what greater extent by endeavouring to trace the 

 interesting chain which evidently connects the Limrtx 

 or common slug, in which the portions of testaceous 

 matter are merely elementary to other molluscs, in 

 which they become small tabular pieces a solid 

 crustaceous substance, a small well-defined shell, par- 

 tially covering- the branchial cavity of the animal's 

 body, and finally a perfect shell, serving as a defence 

 and retreat for the entire body of the animal ; these 

 connecting links may be traced in the Parmacelfa, 

 Tfstacella, Onchidium, Uolabella, and Vitrina, till we 

 arrive at the Helix ; or pursue the reverse course, 

 and trace the links from the perfect Helix down to 

 the L;ma.r, which seems to be the more natural 

 arrangement. In throwing out this suggestion we 

 will lend our assistance, by describing minutely each 

 of the genera we have named as bearing on the 

 question, and to the best of our judgment draw just 

 conclusions by analogous reasoning in those instances 

 where we cannot obtain information from actual 

 observation or the well authenticated researches of 

 competent naturalists. 



LIMACINA (Cimer ; CLIO HELICINA, Linnaeus). 

 Ginelin called this genus of molluscs Helicina, which 

 appears more descriptive of its general characters ; 

 but the name of Limacina, given by Lamarck, has 

 been adopted by succeeding authors. In many re- 

 spects it approximates to the genus Planorbis, particu- 

 larly in having a very wide umbilicus, formed by the 

 flat spread of the whorls. The shell is thin, fragile, 



and papyraceous ; its whorls spiral as in the common 

 Heliv, but united in a discoid form. The body of 

 the animal is of an oblong form, with two branchial 

 fins situated at the base of the neck; the posterior 

 part of the body spiral. This genus differs in few 

 particulars from the Linnaean genus Clio; the animal, 

 however, possesses the power of retreating completely 

 within its shell, which is not the case with the Clio. 

 The Limacina inhabits the North Seas, and is classed 

 by Lamarck as the second genus of the fifth order 

 Pteropoda or winged feet. De Blainville has called 

 this genus Spiratclla; he observes that the characters 

 were taken from Captain Scoresby's Voyages, and 

 are established on an almost microscopic animal 

 found in the Arctic Seas. 



LIMACINEA. The third family of the first order 

 Pulmobranchmla, first class Cephalophora. It includes 

 the genera Succinea, BuHnus, Ac/iatina, Clausilia, 

 Pitppa, Anastoma, Heli.r, Carocolla, Helicolimajc, Tes- 

 tncella, Parmacclla. Limacina, Limax, and Orchidium. 

 The form of the animal is very various: the head, 

 provided with two pairs of tentacula, completely 

 retractile within the animal's body, the posterior pair 

 larger than the other pair, and bearing the eyes at 

 their extremities ; one tooth on the upper lip ; the 

 tongue or lingual mass is small, and covered with a 

 skin thickly set with microscopic teeth or bristles. 

 The shells of these genera, which constitute the family 

 Limacinea, are as different in their form as the ani- 

 mals inhabiting them, the one occasioning the other, 

 but their general characters never vary ; in many 

 respects, such as being always spiral, of an oval or 

 globular form, more or less discoid or compressed ; 

 the summit of the whorls smooth, always without an 

 epidermis ; the aperture round, semilunar, oval, or 

 angular, but never notched. The animals inhabiting 

 these genera are all terrestrial, and feed on vegetables 

 generally, such as fruit or other soft substances which 

 admit of being reduced by the action of the tongue 

 in licking them. The garden snail in this, as well as 

 many other instances illustrative of the structure and 

 habits of a considerable portion of molluscs, may 

 constantly and easily be seen ; and a reference to the 

 article HELIX will further explain some of the daily 

 habits of all similarly constructed animals. The great 

 number of terrestrial molluscs that exist in every 

 climate, and their beauty and usefulness in almost all 

 countries, have excited considerable interest, and 

 occasioned consequently many ample and minute 

 descriptions of their species. Several eminent natu- 

 ralists have attempted a general classification, in 

 which, however, a contrariety of opinion must ever 

 exist ; but the late Baron de Ferussac appears to 

 have reconciled most of the disputed points. His 

 splendid work on Terrestrial Molluscs must ever be 

 viewed as a masterly and elegant production, and 

 will be handed down to posterity a monument worthy 

 of his great name as a profund naturalist, enlightened 

 scholar, and amiable man. In the genera contained 

 in this family, we have preserved in our order of 



! enumeration the usually received arrangement of 

 modern naturalists, without disputing its general ex- 

 cellence ; and in such instances as have occasioned a 



(slight difference of opinion, we have frankly expressed 

 our reasons for dissenting from such high authorities, 

 not in a spirit of srlf-sufficiency, but rather to throw 

 out an useful hint by which the difficulties now sur- 

 rounding the study of malacology may in some degree 

 be lessened, and a lure held out to our readers to 



