MOLLUSCA. 75 



sion could possibly take place. Some changes might be oc- 

 casioned by it, but much practical difficulty would be avoided. 

 Indeed, so useful is the distinction, that conchologists, with- 

 out avowing the propriety of the principle, have in many 

 instances observed it. 



Having thus taken a short view of the different characters 

 employed by conchologists in the arrangement of the tes- 

 tacea, and endeavoured to ascertain their relative import 

 ance, we shall conclude this part of the article by an appli- 

 cation of the principles we have established, to an examina- 

 tion of the Linnaean genera, and to an enumeration of those 

 genera which subsequent naturalists have formed, without, 

 however, attempting to give even an approximation to many 

 of the modern divisions, which have been multiplied beyond 

 all bounds ; as our present object is to convey to the reader 

 some farther remarks, illustrative of the history of the science, 

 rather than specific descriptions. 



LINN^AN GENERA. 



1. CHITON. The only change which has taken place in 

 this genus, of any consequence, is its transference to the 

 naked cephalous mollusca, effected by Lamark. The inha- 

 bitants bear a near resemblance to those of the genus patella, 

 and belong to the order cyclcbranchia of Cuvier. The mar- 

 ginal ligament which connects the testaceous plates, even 

 after the extraction of the animal, is, in fact, the margin of 

 its cloak, and offers, in connection with the notches of the 

 plates, more certain and convenient distinctions for the dis- 

 tribution of the species, than the number or appearance of 

 the valves, a character exclusively employed by Linnaeus. 



2. LEPAS This genus has undergone several important 



