PALUDINID^E. 209 



(Lam.). The shell is triangular-oblong, the operculum 

 calcareous and solid. This genus inhabits waters 

 which have a stony or gravelly bottom. They are 

 often encrusted with a calcareous matter; they are 

 sluggish in their habits, but their tentacles appear to 

 be always in motion. They feed on vegetables. 

 Their eggs are generally deposited on the shell, and 

 carried there till hatched. The eggs are round, of a 

 yellow colour, and provided with a leathery covering 

 which splits in two when the fry are excluded, the 

 upper half being detached, and the other part left 

 adhering to the parent-shell. Moquin Tandon says 

 the eggs are deposited in a cluster of fifty or sixty. 

 The length is 0^35, the breadth 0*25. They are 

 oviparous. 



The family Paludinidcz are more active in their 

 habits than the last-named division ; they are ovo- 

 viviparous. They occasionally float. They are the 

 largest of our fresh- water univalves. The males are 

 smaller than the females. 



Paludina (Lam.) has the eyes on short pedicles ; 

 the operculum is horny. P. contecta has the body 

 dark gray or brown with yellow specks, the head 

 small, the eyes round and black, the foot cloven. 

 The shell is conical, yellowish, with sometimes a green 

 or brown tinge with brown bands, a thick epidermis, 

 a thin operculum. It is marked with concentric 

 striae and lines of growth. It adheres to stones or 

 wood, but when touched falls off. It is sometimes 

 2 inches long, and if inches broad. P. vivipara has 

 the body of a darker colour, the snout broad, and the 

 tentacle blue-black with yellow spots. The male is 

 p 



