Bulletin 5 329 



152 FOSSIL SHELLS. 



MACTRA. 



Two or three mutilated specimens of a species 

 closely allied to M. lateralis, nobis, but too imper- 

 fect to determine the degree of proximity. 



AMPHIDESMA. 



A. subovata. PI. x. fig. 10. Shell transversely 

 ovate-oval, with somewhat prominent and regular 

 concentric striae. 



Description. Shell compressed : beaks rather 

 before the middle, but little prominent : a^iterior 

 submargin with an obsolete, obtuse undulation : 

 lunule lanceolate : cardinal and lateral teeth pro- 

 minent. 



L,ength seven-tenths of an inch, breadth less 

 than one inch. 



CORBUI.A. 



I. C. cuneata. PI. xiii. fig. 2. Shell transversely 

 ovate-trigonal, acutely angulated or somewhat ros- 

 trated before, and depressed on the anterior slope, 

 which is separated from the disk by a subacute 

 line : surface of both valves similarly striate with 

 equal, elevated, equidistant lines, forming grooves 

 between them ; the striae on the smaller valve are 

 rather more distant : umbones not prominent. 



[J. A. N. S., Phila., ist Ser., Vol. IV, 1824.] 



