66 On the Identity of Cyclas elegans, &c. . 



pared to the P. dubium, it is less elongated, less robust, less 

 heavily marked, and differently colored. Found in plenty. 



X. — On the Identity of Cyclas elegans Adams, with Cyclas 

 rhomboidea Say. 



By Temple Prime. Read September 5, 1853. 



In 1822, Say published as follows, in the Jour, of the Acad, 

 of Nat. Sci., vol. ii., page 380 : — 



" Cyclas rhomboidea. — Shell transversely orbicular, rhombiform, sub- 

 equilateral, pale with elevated somewhat transverse lines, umbo not promi- 

 nent. 



"Long, more than one quarter of an inch. It inhabits Lake Cham- 

 plain. It is probable this species attains a larger size than the two spe- 

 cimens from which the above description was taken, and which were 

 found by Mr. Augustus Jessup ; it is distinguishable from the similis by 

 its more rhomboidal form." 



Like many other of Mr. Say's species, that are not accompa- 

 nied by figures, this species has never been properly identified. 



The young of the shell figured in Gould's Report as C. similis, 

 has frequently been mistaken, owing to its more or less qua* 

 drangular form, for the C. rhomboidea ; but nearly every cabinet 

 seems to have had this species represented by something dif- 

 ferent. 



In 1851, Adams sent me a Cyclas from Lake Champlain, 

 which he had always looked upon as 0. rhomboidea ; on com- 

 paring it with the original description, I found it necessary to 

 differ from him. 



