- Testa ovata, spiralis, tenuis, umbilicata. Apertura semi-orbicularis, ad labii anterioris apicem subangulata. Operculum corneum.
- Animal fluviatile, branchiatum, viviparum, rostro brevissimo; oculis ad basin externam tentaculorum acutorum 2 appositis; pedis margine antico duplici; lateribus anticè alis parvis instructis; alâ dexterâ involutâ in canalem per quem aqua in tracheam introducitur.
Typus Genericus Helix vivipara, Lin.
- Shell ovate, spiral, thin, umbilicated. Aperture nearly orbicular, slightly angulated at the top of the inner lip. Operculum horny.
- Animal fluviatile, branchiated, viviparous; rostrum very short; eyes placed at the external base of two pointed tentacula; anterior border of the foot double; on each side the fore part of the body a small wing; that on the right side is folded into a channel, by which the water is introduced into the respiratory canal.
Generic Type Viviparous Snail Pennant.
The common Shell above quoted, inhabiting many of our rivers, will serve as an excellent example of this genus, which is not numerous, and confined to fresh waters; the animals, inhabiting the European species, appear to have been thoroughly investigated by the continental naturalists; and from their account of its singular construction, the above description has been framed. Science should make no distinction of persons or countries; but it is rather mortifying to observe, that these important discoveries in the organization of animals, are pursued with zeal and ability by foreign naturalists, while most of our own content themselves with expatiating on its impossibility, and even go so far as to hint its uselessness, because we can never become acquainted with the animals of all the species of shells in our cabinets: so far this latter part of the argument is most true; but, to ascertain, for instance, the animal of the Cowry, it is surely not requisite we should see those of all the species (near 80 in number), before we venture to describe it? any more than it is necessary completely to dissect every species of Locust before we pronounce it to be one. Science would, indeed, receive incalculable and lasting benefit, if those of our conchologists who reside near the coast would pay greater attention to the inhabiting animals, and less to the shells, of their neighbourhood; for the first would supply that information they acknowledge is so desirable, and the latter would prevent our indigenous Catalogue from being crowded with many dubious, and even foreign shells.
English conchologists appear not to be aware of the vast number of testaceous animals which are now known. Among those truly eminent men who have prosecuted this study, M. Adanson stands foremost, in having minutely described all those he found on the African coast; in the magnificent work of Poli nearly all the Mediterranean bivalves are exquisitely figured; and those of the land and fresh water will receive complete illustration from M. Ferrusac. Cuvier, Lamarck, Say, and even our own countrymen, Dr. Leach and Montague, have all contributed, more or less, to form a mass of information which it is full time should be employed as the basis of natural classification.
Long-spired River Snail—upper and lower figures.
- P. testâ olivaceo-fuscâ, fasciis castaneis ornatâ; spirâ productâ, attenuatâ, aperturâ multo longiore; apice acuto.
- Shell olive brown, with chesnut bands; spire lengthened, attenuated, much longer than the aperture; tip acute.
Inhabits the rivers of India. It is rather thicker than most of the others, and the umbilicus nearly obsolete.
Olive River Snail—side figures.
- P. testâ subventricosâ, totâ olivaceâ; apice acuto; spiræ et aperturæ longitudine æquali; umbilico clauso.
- Shell subventricose; uniform olive; apex of the spire acute; aperture and spire of equal length; umbilicus closed.
Distinguished from the Helix vivipara of authors, by having a less convex, and more pointed spire, hardly any umbilicus, and no bands. Inhabits China.
Carinated River Snail—middle figures.
- P. testâ parvâ, olivaceâ; spirâ aperturâ longiore, apice obtuso, rufo; anfractu basali medio leviter carinato; umbilico obsoleto.
- Shell small, olive; spire longer than the aperture; the tip obtuse, rufous; basal whorl slightly carinated in the middle; umbilicus obsolete.
A distinct species, which is never found larger than the figure. I once saw near 100, which had been picked up on the banks of the Ganges; the spire is rather lengthened, always obtuse, and the umbilicus even less than the last.