44 LEPAS. 



cipal essential characters, being niultivalve, and 

 parasitical ; and the species pass gradually from 

 one conformation to the other in so connected a 

 series, that it would seem needless, and indeed de- 

 structive of simplicity and order, to separate or dis- 

 arrange them. The aperture in the conical divi- 

 sion increases proportionably to the growth of the 

 shell, by means of the extension, in width, of the 

 triangular parts between the valves. The pedun- 

 cled species are called Barnacles, from a strange 

 I)rejudice formerly entertained, that they were 

 transformed into geese ; originating perhaps in 

 their feathery tcntacula, and in their being ob- 

 served moving about on their long flexible tubes 

 above the surface of the water. Both divisions are 

 invariably attached to extraneous substances, usu- 

 ally in groups. 



The genus takes its name either from Xsttuc, the 

 rock, to which the shells adhere, or from Xsttx: the 

 denomination bestowed by the ancients on the 

 family of Patella?, on account, probably, of the 

 ^CG^e-like manner in which they are adherent. 



