CYCLADiE. 287 



Var. More ventricose, and produced at the urn- 

 bones. 



Inhab. ponds, north of England. 



Animal white; siphonal tube very short, broad, 

 and flat, truncated at the end, and seldom protruded 

 much beyond the edge of the shell. 



This species may generally be readily distinguished 

 from others of the genus by its more compressed and 

 oval form, and its cinereous colour. It is the largest 

 of the minute species. (Alder.) 



Length 2-10ths, height 7-40ths, thickness 5-40ths 

 of an inch. 



The genus Cyrena is now no longer found alive 

 in this country, but it must have lived here at no very 

 great period of time (geologically considered), for 

 it is found abundant fossil at Grays, in company with 

 a quantity of other fresh-water and land shells, all 

 now found alive in the neighbourhood, as Pisidium 

 amnicum, Valvata obtusa, &c. &c. (See Introduction, 

 p. 40.) 



