19] 
UNIO crassiusculus, 
TAB. CLXXXYV. 
Seec. Cuar. Oblong-elliptical, depressed; valves 
thick ; surface marked by lines of growth ; 
hinge strong. 
"Tur surface of this shell is regularly curved, without 
any hollow or rising: the beaks are sharp, a little re- 
curved: the lines of growth are not very prominent, 
except two or three of them near the edge : the hinge is 
light and elegant in comparison to that of U. crassissi- 
mus, although thick. 
I am indebted to the Rev. G. R. Leathes for the know- 
ledge of this Unio: he has obtained it from the Craig at 
Bawdesey, in Suffolk. 
The yalves have been replaced by carbonate of lime 
of a crystalline texture, and are attached to masses of 
ochraceous limestone, or lie loose in the craig. 
