i6 



Bryant Wai^ker 

 Section PHYSA s. s. 



Shell smooth. 



^^ 



Fig. 42 Fig- 43 



Type: Bulla fontinalis L. 

 Example : P. gyrina Say, fig. 42. 

 Radula : P. humerosa Gld., fig. 43. 

 Animal: P. heteroxtropha Say, fig. 44. 



Section COSTATELLA Ball, 1870. 

 Shell longitudinally costate. 

 Type: P. costata Newc, fig. 45. 



Genus APLEXA Fleming, 1822. 



Fig- 44 



Fig. 45 



Shell sinistral, elongated, slender, smooth, shining; spire acute; lip 

 simple, sharp, columella but slightly twisted. 



Animal similar to that of Physa, but with the inner edge of the mantle 

 simple, not digitate nor reflected over on the body whorl. 



M 



Fig. 46 Fig. 47 Fig. 48 



Type: Bulla hypnorum L., fig. 46. Radula, fig. 47. Animal, fig. 48. 



Family ANCYLID^. 



Shell patelliform or dextrally spiral, neritiform or planorbiform. 



Animal (fig. 49) sinistral or dextral, with a large oval foot; 

 tentacles short, blunt, cylindrical; eyes sessile on their inner 

 bases ; jaw in three parts or the whole segmented in plates ; radula 

 with the teeth arranged in rows nearly horizontal or slightly 

 curved, central tooth small, unicuspid or bicuspid, laterals bi- 

 cuspid or comb-like, marginals comb-like or subobsolete. Fig. 49 



