198 



bular, extremely ventricose; opening ear-shaped ; the 

 spire depressed; and the circumference of the last 

 whorl at least four times the size of the preceding 

 evolutions. 



These shells are closed by an operculum, sometimes 

 of a horny and occasionally of a calcareous substance, 

 which circumstance, as well as the slight groove on the 

 columella, into which it fits, appears to have escaped 

 Lamarck's observation. 

 Ampullaria Guyanensis Ampullaria Guinaica 



• • • rugosa virens 



fasciata carinata 



canaliculata avellaua 



effusa intorta 



Ampullaria fragilis. 

 [There are several fossil species described in the An- 

 nates du Museum, p. SO.] 



s 



NAVICELLA. 



NERITA PORCELLANA. Chemnitz. 



Chem.% tab. 124, fig. 1082. 

 These are fresh water shells, and nearly allied to Uie 

 Nerita, but yet more closely to the Ncritina. The sum- 



