SHUMARD——TERTIARY AND CRETACEOUS FOSSILs. 121 
ed near the anterior margin, convex, rather aecoagene hee incur- 
ved ; surface marked with fine, rather indist: concentric 
ese p - somewhat 
Although the collection contains y specimens, not 
of them retains = original form, all ie more or less ya 
ted ay pre 
In a few aE st the posterior slope exhibits be — 
carina on only one of the valves and a single exte on 
the other, but weeny: there are two carinz on onl 
shell 
Our shi mbles C. densata oe a from m which it is 
istingui U by the double carina on side and 
its thinner val | 
Form. & — yabendiet} in the 
—This spe is exceeding 
ar’ mi ms lisle ot Deva Goel Mina and ax sho’ Cod 
preariagh woen F where it is associated with Lucina 
and Cerith ra named 
