MOLLUSCA. 113 



of this genus, the lacustris andftuviatilis, natives of Bri- 

 tain. 



The genus PATELLA, as circumscribed by Lamark, has 

 been already sufficiently noticed. The common limpit may 

 serve as the type of this genus. 



In the genus FISSURELLA, established by Bruguiere, 

 there is always an opening like a key-hole, near the summit 

 of the shell. The F. grceca and apertura are found on our 

 coasts. 



The genus EMARGINULA is readily distinguished by the 

 slit or indentation which occurs on the posterior margin of 

 the shell. 



In the genus CAPULUS of Montfort, the shell is conical, 

 with the summit produced into a beak, more or less recurv- 

 ed, and twisted. The P. hungarica of Lister is the type. 

 . The genus CONCHOLEPAS is furnished with an opercu- 

 lum, and in form and habits approaches the buccinum. It 

 is represented by the P. Integra of Da Costa's EL tab. 2. 



fig. .7. 



In the genus CREPIDULA, the cavity of the shell is par- 

 tially interrupted by a simple diaphragm. The P. parcel- 

 lana is the representative of this genus. The C. chinen- 

 sis inhabits the British seas. 



In the preceding genus, the first approach to the turbi- 

 nated shell makes its appearance, which becomes more ob- 

 vious in the genus CALYPTR^A, in which the cavity is fur- 

 nished with a spiral diaphragm. The C. equestris is tht 

 type of the genus, which is related in part to the trochi. 

 From this genus of Lamark, Montfort has separated the IN- 

 FUNDIBULUM, as possessing a central spiral pillar. Sow- 

 erby has figured several species of this last genus in his 



