19 
CYPRINA planata. 
TAB. DCXIX. 
Spec. Char. Cordiform, rather compressed ; sides 
flattened towards the ventral margin ; beaks 
large, not very prominent ; lunette nearly flat,, 
imperfectly defined ; hinge-slope flattened, 
broad ; between the hinge-slope and each 
side is a slightly depressed area; the principal 
tooth in the right valve narrow. 
Ihe length and breadth are nearly equal ; the greatest 
thickness of the united valves is near the beak ; the sur- 
face is smooth, excepting near the margin and upon the 
area on the sides of the hinge -slope, where the lines of 
growth form irregular furrows ; the hinge-slope is so 
flattened, that the specimen will stand upon it as upon 
a base. 
Several examples of this handsome large fossil have 
been found by Mr. Prestwich at Basingstoke, and small 
individuals have been discovered in the clay at Brentford 
and in Brackiesham Bay. 
