PALUDINIDiE. 



This family of fresh-water Mollusks is nearly allied to 

 Littorina and its associates. With the Neritidce it is con- 

 nected through the intermediate exotic group of which 

 Ampullaria is a member. Muzzle-shaped heads, produced 

 tentacula, sessile or nearly sessile eyes, round or ovate entire- 

 niouthed turbinated shells characterize the assemblage. 

 The species it includes are distributed all over the world, 

 inhabiting lakes and streams. All are operculated ; the 

 opercula are in most of them formed of concentric laminae 

 ranged round a variously-placed nucleus. Many of the 

 Paludint are among the largest of fluviatile univalves, 

 others among the smallest. Some are brilliantly-coloured, 

 but usually they have a dingy brown, horn-coloured, or 

 greenish epidermis. Species of all the following genera 

 range as far back in time as the oolitic period, and the 

 forms assumed by the most ancient of them closely resemble 

 those of existing members of the tribe. 



PALUDINA, Lamarck. 



Shell turbinated, with a produced spire, whorls usually 

 rounded, surface covered with a coloured epidermis ; mouth 

 more or less oval, sometimes nearly round, slightly angular 

 above, peristome thin, continuous. 



Animal with a lengthened muzzle ; head bearing two 



