GASTEROPODA PECTINIBRANCHIATA. 261 



PALUDINA, Lam. 



This genus has lately been separated from the Cyclostomse, 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 ani- 

 mal, being provided with 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 wing on each side of the fore part of the body. The anterior 

 edge of the foot is double, and the wing of the right side forms a little ca- 

 nal which introduces water into the respiratory cavity, the incipient indica- 

 tion of the siphon in the following family. 



The Ocean produces some shells which only differ from the Paludinse in 

 being thick. They form the 



LITTORINA, Feruss. 



Of which the common species, Le Vigneau Turbo littoreus, L., abounds 

 on the coast of France, where it is eaten. The shell is round, brown, and 

 longitudinally streaked with blackish. The 



PHASIANELLA, Lam. 



An oblong or pointed shell, similar to that of several Bulimi and Lymnsese; 

 the aperture also higher than it is wide, and furnished with a strong oper- 

 culum; base of the columella sensibly flattened, but no umbilicus. 



They inhabit the Indian Ocean, and are much sought for by collectors on 

 account of the beauty of their colours. The animal is provided with two 

 long tentacula, with eyes placed on twotubercles at their external base, and 

 with double lips that are emarginated and fringed, as well as the wings, 

 each of which has three filaments. 



AMPULLARIA, Lam. 



A round, ventricose shell, with a short spire, as in most of the Helices; the 

 aperture higher than it is wide, and provided with an operculum; the colu- 

 mella umbilicated. 



They inhabit the fresh or brackish waters of hot countries. The animal 

 has long tentacula, and eyes placed on pedicles at their base. 



HELICINA, Lam. 



Judging by the shell, the Helicinze are Ampullariae in which the margin 

 of the ap'erture is reflected. 



MELANIA, Lam. 



A thicker shell; the aperture, higher than it is wide, enlarges opposite to 

 the spire; the columella without plicae or umbilicus; length of the spire very 

 various. 

 The Melanis inhabit rivers, but are not found in France; the animal has 



