20 C O N C H O L O G Y. 



judicious NaturaUft fliall always be ca^ 

 pable of dijftinguifliing the fpecies by the 

 Shells alone, though he has many of the 

 fame kind, of very different appearances, 

 before him : for every fpecies has one 

 or more particular fpecific charafler, either 

 in work, colour, or fubitance, iifc. which 

 it retains through all its various flages 

 and forms, and therefore is always to be 

 *di(linguiflied and known by it. 



Mr. Adanfon drew a conclufion of the 

 different Shells he propofes for the fpecies 

 of the Bhick Limpet, from the fituation 

 of its eye or beak being at two thirds 

 of the length of the Shell. This fitu- 

 ation of the eye, he, for want of accu- 

 racy, thought to be a particular charafter 

 of the Black Limpet : but he overlooked, 

 or did not know, that the eyes or beaks 

 of many other fpecies of Limpets. are 

 placed in like manner, or at two-thirds of 

 the length of the Shell. He therefore erred 

 as much ia making that particular the 



criterion 



