159 



Crepidula fornicata 



porcellana 



aculeata 



Crepidula unguiformis 



dilatata 



Peruviana. 



ANCYLUS. 



PATELLA LACUSTRIS. Lillll. 



Sowerbys Genera, No. 1 4. 

 Draparnaud was the first to constitute this genus, 

 and separate it from that of Patella, preserving the 

 name given it by Geoffroi, which Lamarck has conse- 

 quently adopted. The shell is of a thin, brittle, and 

 membranous texture, in the form of an oblong cone, 

 with a pointed summit inclined backward; the base 

 oval and smooth. It is a fresh water shell, and La- 

 marck observes he has only provisionally placed it with 

 the Calyptraeee: the animal's existing in fresh water, 

 and habitually breathing the air, renders it very dif- 

 ferent from the inhabitant of the latter, with which it 

 is here associated. 



Draparnaud has placed this genus following that 

 of Lymnaea, to which the animal more nearly approxi- 

 mates in its organization. 



