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 Linnzean 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. 
LINNZAN GENERA. 
1. Curron.—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 cyclobranchia 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 Linnzus. 
2. Lepas.—This genus has undergone several important 
