91 
HIPP0P0D1UM. 
Gen. Char. An equalvalved obliquely transverse 
bivalve ; valves inflated,, subbilobed ; one rug’" 
ged tooth at the hinge ; cartilage external. 
The beaks of the Hippopodium are much incurved, 
and behind them there is a deep heart-shaped cavity ; 
the anterior slope is deeply sunk between the anterior 
lobes of the two valves. The cartilage of the hinge is 
external and elongated. In the left valve there is one 
thick rugged tooth beneath the beak, and only a small 
indication of a remote one beneath the cartilage. 
The Rev. W. D. Conybeare first distinguished this 
genus, and named it in his M. S. catalogues. At pre- 
sent only one species is known, and of that the speci- 
mens hitherto found are not enough freed from the stone 
to shew the situation or number of the muscular impres- 
sions, or the tooth of the right valve, if it have one. 
HIPPOPODIUM ponderosum. 
TAB. CCL. 
Spec. Char 
Syn. A bivalve fossil from Colebrook Dale. 
Rashley’s specimens of Minerals, tab. xx. 
A very gibbose, rugged, and heavy shell : the lines 
of growth are strongly marked by irregular obtuse 
ridges. The anterior lobe is somewhat angular, and a 
little pointed ; the posterior lobe much smaller, rounded, 
and as it curves with the beak it forms the boundary of 
the heart-shaped pit beneath it : this pit is deep, and 
