58 
MOLLUSCA. 
Paludina, Lam. 
This g’cnus has lately been separated from the Cyclostompe, because 
there is no ridge round the aperture of the shell ; because there is a 
small angle to that aperture as well as to the operculum, and finally, 
because the animal, being provided Avith branchiae, inhabits the 
water, like all other genera of this family. It has a very short snout 
and two pointed tentacula ; eyes at the external base of the latter, but 
on no particular pedicle, and a small membranous Aving on each side 
of the fore part of the body. The anterior edge of the foot is doid^le, 
and the Aving of the right side forms a little canal Avhich introduces 
Avater into the respiratory cavitv, the incipient indication of the siphon 
in the folio Aving family. 
The common species, Helix vivipara, L. ; Drap., I, 16, Avhose 
smooth and greenish shell is marked Avith tAvo or three purple, 
longitudinal b nds, and Avhich abounds in stagnant Avatcrs, in 
France, produces living young ones ; in the spring of the year 
they may be found in the oviduct of the female, in every stage 
of development. Spallanzani assures us that if the young ones 
be taken at the moment of birth and be reared separately, they 
Avill reproduce without fecundation, like those of . the Aphis. 
The males, hoAvever, arc nearly as common as the females ; they 
have a large penis Avhich jtrotrudes and retracts, as in Helix, 
but through a hole })ierced in the right tentaculum, a circum- 
stance Avhich renders that tentaculum apparently larger than 
the other, and Avhich furnishes us Avith a mode of recognizing 
tlie male A 
The Ocean produces some shells Avhich only differ from the Palu- 
diiicC in being thick. They form the 
Littorina, Feruss., 
Of Avhich the common species, Le Vigneau — Turbo liftoreus, L., 
Chemn. V, cIxxxa', 1852, abounds on the coast of France, AA'here it is 
eaten. The shell is round, broAvn, and longitudinally streaked Avith 
blackish. The 
T^I oxoDox^ Lam. 
Only differs from Jnttorina in having a blunt and slightly salient 
tooth at the base of the columella, Avhich sometimes has also a fine 
notch. The external edge of the aperture is crenulated in several 
species. The animal is more highly ornamented, and is generally 
furnished Avith three or four filaments, on each side, as long as its 
tentacula. The eyes arc idantcd on particular pedicles at the exter- 
nal base of the tentacula ; the o])erculum is round and horny. 
♦Add, Cydost. achafinvin, Drap. I, 18; — C. impunan, Id., 19, 20, or Helh' 
tentaculata, L., iXc. ; and the small species of salt-v'ater ponds described by Beii- 
dant, Ann. dn ISIiis., XV, p. 199. 
