184 PROCEEDINGS OF THE ACADEMY OF 



curve of the beaks to their points, and downward to the anterior 

 basal angle; while within this area there is a smaller, deep, and 

 sharply defined impression, or second lunule, under the beaks; 

 basal margin forming a nearl}' semiovate curve from the lower ex- 

 tremity of the large lunule to the posterior end of the valves. 

 Surface ornamented by small, nearly regular radiating costse, 

 separated hy rather broader furrows ; the whole being crossed by 

 larger concentric ridges and furrows, which become smaller, more 

 regular, and rather more distinct on the large lunule, where there 

 are no radiating costse. 



Length and height, each 1 inch; convexity, 0.86 inch. 



Of this curious form I have seen but one specimen, wliich is in 

 the condition of an internal cast. The shell itself must be ver}" 

 thin, as the surface-markings are quite distinct on the cast. In 

 general form, and its strongly incurved beaks, it reminds one of 

 Isocardia, but its radiating costoe, and very large lunule-like 

 cordate impression occupying the whole anterior end of the shell, 

 are peculiar characters, I believe unknown in that genus. In 

 addition to these features, its hinge would seem to have been 

 without the teeth of Isocardia, so far as can be determined from 

 the internal cast. From these facts I strongl}' suspect that it will 

 be found to belong to an undescribed genus. If so, I would 

 propose for it the name Procardia, in allusion to the distinctly 

 heart-shaped impression occupying the whole anterior end. This 

 species is evidently related to Cardium ? decussatum, Mantell, 

 and must belong at least to the same group. It is much smaller, 

 however, and differs specifically in having mere radiating lines, 

 instead of broad costce. 



I am under obligations to Dr. Newberry for the use of the only 

 specimen I have seen, which was given to him b}^ Prof. J. T. 

 Hodge, who bi'ought it from the Upper Missouri countr3\ 



Locality and position. Mr. Hodge discovered the typical 

 specimen in a band of iron ore that extends along tlie U2)per 

 Missouri for some distance, near the Great Bend in the Fort 

 Pierre group. 



[August 15, 



