12 YIVIPARA. 



Family VIVIPARID^. 



[Tongue very short, armed with seven series of teetli 

 (3.1.3); teetlx laminar, longitudinal, ovate, apex recurved, 

 dentate on each side of the tips ; inner lateral tooth broad. 

 Eostrum moderate, entire ; tentacles tapering, with the eyes 

 on tubercles at their outer bases. Mantle simple in front ; 

 gill comb-like, single. 



Operculum anular, regular. 



Shell spiral, turbinate, covered with an epidermis ; aper- 

 ture simple in front. 



The members of this family are fluviatile, inhabiting 

 lakes and streams ; the shells of most of them are dingy 

 broT\Ti, or covered with a green, horny epidermis ; they are 

 distributed nearly all over the world. — H. and A. Ad] 



TIVIPARA, Lam. 



[Animal with a small lobe on each side of the neck. 

 Operculum horny, annular, composed of concentric elements 

 around a central nucleus. 



Shell thin, turbinated, umbihcated ; 

 '^' ■ spire produced, whirls round, smooth 



or carinated, covered with an olivaceous 

 epidermis ; peristome thin, continuous, 

 simple anteriorly. 



The Viviparae inhabit the rivers and 

 lakes throughout the northern hemis- 



Animal of Vivipara. 



phere. The females are ovo-viviparous, 

 and the young fry are not forsaken by the parent until the end 

 of the second month of their existence, by which time the bands 

 of cilia, which ornament their shells, have disappeared. — H. and 

 A. Ad.'\ 



I have had opportunities of studying the habits of no other 

 species than V. decisa and suhcarinata, which are found in great 

 numbers in the Delaware at Burlington, N. J. They live on the 

 muddy bottoms of the river edge, where they are exposed many 



