OF CONCHOLOGY. 91 



on the shore ; and are so tenacious, 

 that they cannot be removed without 

 breaking the shell, unless taken by 

 surprise. Those inhabiting fresh wa- 

 ter are generally found adhering to 

 aquatic plants. The Patellae are 

 called limpets in England. 



The Patella is a very good genus, 

 though there are several authors who 

 dispute this point. We cannot see 

 that the distinctive characters Lamarck 

 has chosen, are sufficient reason for 

 the formation of new genera; their 

 division into sections appears to us 

 quite sufficient ; for with the excep- 

 tion of the chambered limpets, they 

 are all perfectly simple shells, and 

 very like each other. 



Lamarck forms the Patellae into six 

 genera : Patella, Fissurella, Emargi- 

 nula, Concholepas, Crepidula, and 

 Calyptraea. 



In Turton's Linne no less than 240 

 species of Limpets are described ; 



