CONRAD'S NEW FOSSIL SHELLS OF THE UNITED STATES. 299 



SPLENDENS, 



Iridina aplendcns, Clionu, PI. 1, fig. 2. 

 Oblong-subovatc ; anterior lino of cardinal foctli niudi longer than in the preceding, and the shell Ics'? 

 inequilateral; cavity of umbo much lcs.s capacious than in the Macmnitrei. 



This genus at present embraces three specie.s, inhabiting rivers in tropical Africa. 

 Besides the great difference in the hinge, the muscular impressions vary from those 

 of MuTELA, particularly the anterior accessory, which is small and oval, while in tlie 

 latter it is elongated. The difference is as great between these two genera as betvveea 

 Paxyodon and Prisodon, 



Descriptions of new Fossil Shells of the United States. 



By T. A. Conrad. 



Cretaceous Species, 

 INOCERAMUS, Sow. 



Inoceramus perovaljs. pi. 27, fig. 7- — Oval, convex, slightly oblique ; beaks medial, both dorsa marginii 

 equally declining; basal margin acutely rounded; surface with obsolete concentric undulations, 

 J. perovalis, Con. Proceed. Acad. Nat. Sci., vi. p. 200. 



Locality, Chesapeake and Delaware Canal. Mr. Vanuxcm, 



REQUIENIA, Matheron. 



Bequienia Senseni. pi. 27, fig, 8. — Rounded ; both valves profoundly curved ; beaks involute, thg 

 volutions of the larger valve, 3, rounded in both valves. 

 Jnoceramus Senseni, Con. Proceed. Acad. Nat. Sci., vi. p. 200. 



Locality. Missouri river, Nebraska. Mr. Senseny. 



PHOLAS. 



Pholas pectorosa, pi. 27, fig- 9. — Ovate-cuneate ; anteriorly inflated, contracted in the middle; posterior 

 side cuneiform ; disk with radiating ribs, largest anteriorly, and interrupted by concentric furrows; 

 anterior side very short, margin obtusely rounded or subtruncated ; basal margin rounded anteriorly, 

 contracted medially, straight posteriorly 

 p. pectorosa, Con. Proceed. Acad. Nat. Sci , vi, p. 200. 



Locality. Tinton Falls, Monmouth Co., N. J. 



This rare species was found by the late Lardner Vanuxem. It is a cast, on the 

 right valve of which an impressed line runs obliquely from the apex, while on the 

 opposite valve there is a corresponding furrow, and the three ribs nearest the posterior 

 end are more remote from each other, than in the right valve. 



