376 Miscellanies. 



are situated in the high lands of the range, the character of the shells 

 of these rivers is completely the same with those of the western wa- 

 ters. In respect to the land shells, this law of distribution does not 

 hold ; the species of the eastern side being every where equally com- 

 mon on the western. "If it be demanded," says Mr. Lea, "why 

 the line of demarcation should not be as perfect for terrestrial as flu- 

 viatile shells, we might say in answer, that the barrier of a mountain 

 could in time be overcome even by the slowly travelling snail. 

 Surely in the lapse of time, the progeny of those which accidentally 

 began to climb the steeps, might descend into the valleys of the op- 

 posite side." 



• The memoir contains descriptions also of the follov/ing new spe- 

 cies (and one new genus) of other families, which we enumerate, 

 with their localities : viz. 



CoNCHa:. 



Cyrena rotundata. » 



Jayensis. Batavia f 



Wobdiana. Canton. 

 Aphrodite columha. 



COLIMACEA. 



Helix muscarum. Society Islands. 



purpuragula. Java ? 



ovum-reguli. do. 



monodonta. do. 



cyclostomopsis. 



mamilla. - , 



diaphana. 



Himalana. Himalaya Mountains. 



vesica. 



cincta. Java ? 



Woodiana. Near Canton. 



globula. do. 



Helicina lens. Feejee Islands. 

 pulcherrima. Java. 

 virginea. do. 



Achatina Vanuxemensis. Mexico. 

 Succinea retusa. Ohio. 

 Auricula fuscagula. Brazil. 

 Cydostoma striata. Peru. 



