213 
Relations and Differences— species is closely related to tlie 
preceding ; and differs from it only by its external ornamentation, and in its 
proportions. It might almost be considered a variety of the same species. 
Horizon and Localities . — It is found in the same sandstone as E. 
nohilissima. 
Genus — CARDINIA, L. Agassiz. 
Oaedinia exilis, R. McCoy. 
PL XVIII, Fig. 2. 
Cardinia ? exilis, F. McCoy, 184:7, Ann. Mag. Nat Hist., XX, p. 303, pi. 15, fig. 1. 
This is an elongated, oval, depressed shell, much broader anteriorly 
than posteriorly, with a sharp ventral margin. The hinge line is as much 
arched as the ventral margin, to which it is united by an elliptical curve 
bounding the anal or posterior margin. The anterior margin and the beaks 
are united by a curve rendered slightly sinuous by the lunule. The very 
small and nearly straight beaks, anteriorly placed, touch each other; the 
external ligament is rather long, occupying nearly one-third of the length of 
the hinge line. The shell is very solid, having a mean thickness of more 
than two millimetres ; its surface is ornamented with numerous small, 
irregular, concentric lines of growth ; it is black, while the rock in which it 
is preserved is greyish-white. 
Dimensions. — The length is about eight, the breadth four, and the 
thickness two centimetres. 
Relations and Differences. — I could not find the hinge of this 
species, but it lias all the external characteristics of Cardinia, and according 
to McCoy the shape of their pallial and muscular impressions also, so 
that I think I am safe in placing it in this genus. I know no Carboniferous 
species sufficiently like it to be confounded with it. 
Horizon and Localities . — A single specimen of this species was 
found at Wollongong. 
