HI 



ent year Mr. Sowerby has described a third type under the 

 name of C. subrugosum, (Thes. Conch. II. p. 161*, pi. Suppl. 

 31 B. f. 308, 309.) 



Having found some difficulty in identifying these species, 

 I concluded first to study the shells themselves and their oper- 

 cular which are in my collection. Twenty types, which have 

 seemed worthy of notice, are described below. Perhaps two 

 or three of these may be due to accident or circumstances ; 

 but most of them are probably original types. Many of them 

 are local. For the most part they are of less value than is 

 usually assumed for a species. 



■\ 



Sc. 



In the accompanying table we have endeavored to express 

 the affinities and values of the types. In the first column the 

 numbers corresponding to the types described. In the second 

 column they are grouped under fourteen more comprehensive 

 types, which are indicated by the italic letters. In the third 



