82 



In the district under review, viz. : that within a few miles of 

 Sherborne, I have succeeded in obtaining as many as 18 Species, 

 which it is the object of this paper to describe. 



Our species resolve themselves into two natural groups, in the 

 first of which the shell is more or less smooth and possesses some- 

 what fine lines of grcnvth. 



The second division has prominent ribs or ridges which present 

 a somewhat ribbed appearance. 



Sliell with distinct ribs or ridges. 

 9. Adarte excavata (Sow.) 



As the specimens have been obtained for the most part from 



