159 
They may he distinguished from Cyclostoma by the simple la- 
brum^ as well as by other characters of the shell, as also of the 
animal, from Melania by the simple curvature of the labrum at 
at base, and from Yalvata by the form of the aperture which is 
not angulated above in that genus. 
The animal has two linear-acute tentacula, with the eyes at their 
exterior base ; anterior part of the body with a small membrana- 
ceous wing on each side, the right one is recurved in a small 
canal, which introduces the water into the respiratory cavity 'y’ 
the branchiae are composed of parcels of filaments, which are 
attached to the sides of the branchial cavity,^^ and are altogether 
internal, a character which distinguishes them from the animal of 
Valvata. 
They inhabit fresh waters and are very common in almost all 
our lakes and streams. As they respire water, they do not so 
uniformly reside near the water’s edge as the Lymnedc, which 
respire air only. Like them, many of the species, if not all, have 
the power to swim at the surface in a reversed posture, the foot 
being applied to the surface, and the shell being downward. 
Lamarck describes seven recent species, and Defrance enumer- 
ates five fossil ones. 
Paludina deoisa. — Specific character. Aperture more than 
half the length of the shell, within bluish-white. 
Cochlea virginiana e fiava viridescensy non faciatay Lister. 
Conch, tab. VLlyfig. 27. 
Petiver gazophyly tab. 106,^1^. 18. 
Paludina decisay nobis. Nicholson^ s Encycl. (Amer. Editiony) 
article Conchologyy pi. 2, fig. 6. 
Ohs. The species is very common in various parts of the Union. 
Dillwyn informs us that Muller and others have incorrectly quoted 
Lister’s figure for their Helix angularis. PI. 10, the upper and 
lower figures. 
Paludina vivipara, Lin. — Specific character. With about 
three reddish-brown revolving lines. 
Cochlea vivipara fasciata. Fluviatilisy Lister. Conch. y tab. 
126, 26. 
Helix viviparay Linn.y Gmel. and others. 
Nerita viviparay Muller y Verm.y p. 182. 
Cyclostoma viviparay Draparn.y pi. \)fig- 16. 
