1 20 CONCHOLOGY. 



Paludina vivipara. Paludina unicolor. 



P. achatina. P. impura. 



P. Bengalensis. P. muriatica. 



P. viridis. 



P. vivipara. The viviparous Paludina. PI. 21, fig. 1. 



Thin, ovate, ventricose, wrinkled longitudinally ; body with 

 three brown bands : covered with a greenish epidermis ; ap' 

 erture almost round. 



3. Ampullaria. Eleven species. 



This genus is evidently intermediary to the Paludina and 

 the Natica. Its species are probably all fluviatile ; some at- 

 tain a great size. 



Shell thin, globular, ventricose ; umbilicus small, forming 

 a compressed funnel-shaped aperture, without interior callos- 

 ity ; spire very short, the last whorl much larger than all the 

 others together ; aperture ovate, longer than broad, with mar- 

 gins united ; right margin smooth and sharp ; columellar lip 

 thickened, projecting, and reflected over the umbilicus ; oper- 

 culum horny, rarely calcareous, thin, oval, not spiral, with 

 concentric elements ; summit sub-marginal, inferior, passing 

 obliquely by the right edge of the aperture, but attached to 

 the left. 



Ampullaria Guyanensis. Ampullaria Guinaica. 



A. rugosa. A. virens. 



A. fasciata. A. carinata. 



A. canaliculata. A. avellana. 



A. effusa. A. intorta. 



A. fragilis. 



A. Guyanensis. The Guiana Ampullaria. 

 Globular, thick, with unequal longitudinal striae ; covered 

 with brown epidermis ; inside golden colour. 



A. rugosa. The rough Ampullaria. PI. 21, fig. 3. 

 Species dextral. 



A . Guinaica. The Guinea Ampullaria. 

 Species sinistral. 



