114 THE HAMILTON ASSOCIATION. 
hood is narrower and sharper than in C. brevimentum ; attenuated partly 
by loss of substance. 
The notch below is deeper than in the figures quoted, and it has a bold 
outline with an ogee curve. The cast itself has suffered a slight damage 
by having lost some of its convex surface, and the middle part of both its 
ventral and its dorsal edge, when it was being detached from the block. 
With the above-mentioned distinctive characters we may regard it pro- 
visionally as a separate species, with the name of Cypridina antiqua, sp. 
nov. 
This internal mould of a left valve is somewhat decorticated across 
the middle of its convexity. The cast consists of dark-grey, fine-grained, 
and slightly micaceous mudstone, distinct from the limestone to which it 
is attached. It measures 15 millimetres in length and 10 in height (from 
dorsal to ventral edge). 
