160 



The third species, A.spina-rosae, DeFerrusac has sa- 

 tisfactorily proved not to belong to this genus, and La- 

 marck has inadvertently continued Draparnaud's er- 

 ror in supposing it did. See Sowerby's Genera, No. 14, 

 Ancylus lacustris Ancylus fluviatilis 

 Ancylus spina-rosse. 



ACERA. 



Cuvier Ann. duMns. p. 16, pi. 10,/. 15, 16. 



The Acera is a molluscous animal without any testa- 

 ceous covering external or internal, and here classed as 

 preceding others of the same species, which have shells 

 enveloping or covered by their bodies. 

 Acera carnosa. 



«BULLiEA. 

 BULLA APERTA. Linn. 



Chemnitz 10, tab. H6,Jig. 1354, 1355. 

 These shells are nearly allied in many respects to those 

 of the G. Bulla, from which, however, they must be 

 distinguished, not being externally visible, but con- 



