OF CONCHOLOGY. 39 



DESCRIPTIONS OP MIOCENE, EOCENE, AND CRETACEOUS 



SHELLS. 



BY T. A. CONRAD. 



3Iiocene Species. 



PECTINIDu^. 

 PECTEN, Linn. 

 P. CERINUS, Conrad. — PI. 2, fig. 2. 



Description. — Subovate, extremely thin, compressed ; ears 

 equal ; right valve radiately ribbed ; ribs very slightly raised 

 and rounded ; surface ornamented by minute, close divaricating 

 lines, left valve without ribs. 



Locality. — St. Charles Co., Md. Prof. Cope. 



CALLISTA, Adams, (not Poli). 



C. VTRGINIANA, Conrad. — PL 2, fig. 1. 



Description. — Ovate, convex, very inequilateral, substance 

 moderately thick ; lunule long, lanceolate, defined by two slight 

 grooves and distinctly carinated line ; the inner impressed line 

 minute ; these two impressed lines form the raised line which 

 does not rise above the surface of the shell ; summit obtuse ; 

 posterior side produced, subcuneiform ; ventral margin rounded 

 profoundly ; posterior extremity obtusely rounded ; umbonal 

 slope terminal, suddenly rounded; posterior area depressed 

 opposite the umbo, and inferiorly flattened. 



Locality. — Petersburg, Va. 



ARCID^E. 



SCAPHAECA, Gray. 

 S. TENUICARDO, Conrad. — PI. 2, fig. 4. 

 Description. — Elongate-ovate, ventricose ; ribs about 24 to 



