344 AMPULLARIIDJ^. 



in a single, coriaceous, spherical capsule, which is affixed 

 to stones or the stems of aquatic plants. 



Species of Valvata. 



contorta, Midi. naticina, Mke. 



Guatamalensis, Morel. piscinalis, Mull. 



humerosa, Say. pupoidea, Gould. 



inconspicua, Gould. Schmidtii, C. B. Adams. 

 mucronata, Mke. 



Sub-gen. gykokbis, Fitzinger (Planella, Schliit). 



Shell discoidal ; spire depressed, whorls rounded ; umbilicus 

 very wide aud deep. 



annellata, Mke. minuta, Drap. 



cristata, M'ull. pygmgea, C. B. Adams. 



depressa, Pfeiff. spirorbis, Brap. 

 gemma, Ziegl. 



Sub-gen. tbopidina, H. and A. Adams. 



Shell turbinate ; spire elevated, whorls rounded, carinated ; 

 aperture circular. 



bicarinata, Lea. tricarinata, Lesueur. 



Fam. AMPULLARIID^. 



Lingual membrane with seven series of teeth (S'TS), 

 central teeth acute, lateral, subulate. Rostrum divided 

 into tw^o long tentacular lobes in front ; tentacles long 

 and filiform ; eyes on peduncles at the outer bases of the 

 tentacles. Mantle with a more or less elongate siphon on 



