SECTION VIL 137 



the part that contains the fijGi is concave, 

 Imooth, and often finely wafhed with co- 

 lours. The Shell is more or lefs conicaL 

 The apex, or eye, is either whole or per- 

 forated, and is feldom placed exadly in the 

 middle of the Shell, but moft commonly 

 inclines towards one end; that is, takino- it 

 m its longeft dimenfions. The rim of the 

 Shell, which forms its bafe, is likewife 

 various, fometimes without any promi- 

 nencies or fmooth, fometimes with large 

 ones or jagged, and fometimes with flits 

 only, or crenated. Their external furface 

 is often rough and fcabrous, and their 

 apices often imperfed ; for, moft of this 

 family adhering to the rocks, they are much 

 expofed to the fun during ehb, and to all 

 the violences that render dead Shells unac- 

 ceptable to the curious. 



Though it commonly happens, that 

 the Shells rriod remarkable for the bril- 

 liancy of their colours are of the fimpleft 

 form, as the Nerits, Olives, Volutes, Sec. 

 yet this tribe feems an exception. It is true 



ther^ 



