640 CRETACEOUS PALEONTOLOGY. 



Corbula foulkei Lea. 

 Plate LXXIL, Figs. 23-26. 



1861. Corbula foulkei Lea, Proc. Acad. Nat. Sci. Phil. (1861), 



p. 149. 

 1864. Corbula foulkei Meek, Check List Inv. Eoss. N. A., Cret. 



and Jur., p. 15. 

 1868. Corbula fowlkii Con., Cook's Geol. N. J., p. 727. 

 1886. Corbula subcompressa Whitf., Pal. N. J., vol. i (Monog. 



U. S. G. S., vol. 9), p. 180, pi. 23, fig. 26. 

 1905. Corbula foulkei Johns., Proc. Acad. Nat. Sci. Phil. 



(1905), p. 17. 



Description. — The dimensions of a nearly complete individual, 

 a plaster cast taken fro'm a natural mould, are : length, 12.5 mm. ; 

 height, 9 mm. ; thickness, 6 mm. The dimensions of the perfect 

 internal cast of the same individual are : length, 1 1 mm. ; height, 

 8 mm.; thickness, 5.5 mm. Shell subtriangular in outline; the 

 beaks slightly in front of the center, moderately incurved, point- 

 ing a little forward. Hinge-line arcuate; anterior and posterior 

 cardinal margins sloping symmetrically on either side of the 

 beak, and meeting at an angle of about 122°; anterior margin 

 rounding from the cardinal intO' the basal margin ; basal margin 

 moderately convex, curvingf upward more abruptly in front than 

 behind; postero-basal extremity angular; posterior margin 

 obliquely truncate, meeting the post-cardinal margin in a broadly 

 obtuse angle. Valves moderately and subequally convex, with 

 an angular umbonal ridge; middle portion of the valve gently 

 convex, the surface curving somewhat abruptly tO' the antero- 

 cardinal margin; post-umbonal slope narrow, concave, rather 

 abrupt. Surface of shell marked by inconspicuous lines of 

 growth. In the internal cast the beaks are broader and blunter, 

 and the left valve seems tO' be slightly more convex than the 

 right; the muscular impressions are strongly impressed, indi- 

 cating a thickening of the shell at these points, and giving to 

 the area between them and the pallial line a somewhat inflated 

 appearance. 



