154 



verse striae; a deep and narrow marginal fissure, ex- 

 tending nearly half way to the summit. 



Most of the shells of this genus are very small; some 

 are of an elevated, and others of a widely depressed co- 

 nical form. 



Emarginula fissura Emarginula rubra. 

 [And three fossil species.] 



FISSURELLA. 



PATELLA PICTA. Gmellll. 



Mart. 1, t. 11,/ 90. 



This is another division of the Linnsean Patellae: the 

 shells are in the form of a very depressed truncated 

 cone, elliptical or oblong, perforated at the summit; the 

 margin thickened, and sometimes crenulated: the per- 

 foration is never perfectly round, but generally of an ob- 

 long or oval shape, and very frequently resembles a 

 key-hole, from which circumstance they are called 

 Key-hole Limpets by English collectors; the exterior 

 surface longitudinally ribbed, and slightly striated 

 transversely. 



