188 POPULAR CONCHOLOGY. 



55. Valvata. — Shell cone-shaped, or flat- 

 tened; whorls rounded and h 

 distinct; mouth round, or ^ 

 nearly so, with the lips united 

 and acute; an operculum. 

 Animal having a very distinct head, prolonged 

 into a kind of proboscis, and furnished with two 

 very long tentacula, with eyes at the base; 

 foot short. — There are 6 species recent, and 2 

 fossil. 



Found only in rivulets and ponds in Europe 

 and North America. 



56. Paludina. — Shell cone-shaped, having 

 the whorls rounded ; aperture round- 

 ish, angulated above ; margins of the 

 inner and outer lip united ; operculum 

 horny ; shell covered by an epidermis. 

 Animal, head furnished with a pro- 

 boscis, and two tentacula having eyes at the 

 base; foot rather triangular. — 21 species re- 

 cent, and 13 fossil. 



This genus is distributed all over the world, 

 and is usually found in fresh waters, rivers and 

 ponds ; there are, however, some species found 

 in salt marshes, but none in the sea. 



