638 CRETACEOUS PALEONTOLOGY. 



extremity angular; posterior margin nearly vertically truncate, 

 sometimes slightly oblique; the post-cardinal extremity angular 

 or subangular. Surface of the valves strongly convex from the 

 dorsal to the ventral margins, slightly convex longitudinally 

 across the greater portion of the central part of the shell, and 

 curving rather abruptly to the anterior margin ; an angular um- 

 bonal ridge passes from the beak to the postero-basal extremity; 

 the post-umbonal slope abrupt, usually a little concave; the pos- 

 terior extremity of the right valve compressed and a little pro- 

 duced. Surface of the shell, as seen in impressions of the exterior, 

 marked by rather fine, more or less irregular, concentric lines of 

 growth, which become more conspicuous near the ventral margin 

 and upon the post-umbonal slope. In the casts the surface is 

 smoother, the umbonal ridge is less angular and the muscular 

 impressions are inconspicuous. 



Remarks. — This is the commonest member of the genus in the 

 nodules at Lorillard, and can be recognized from all other 

 species in New Jersey, by its elongate form, with the dorsal and 

 ventral margins more or less subparallel. 



Formation and locality. — Woodbury clay, Lorillard (102), 

 near Haddonfield (164). 



Geographic distribution. — New Jersey. 



Corbula bisulcata Conrad. 



Plate LXXIL, Figs. 15-22. 



1875. Corbula bisulcata Con., Kerr's Geol. N. Car., App., p. 11, 



pi. 2, figs. 13-14. 

 1886. Corbula Poulkei AVhitf., Pal. N. J., vol. i (Monog. U. 



S. G. S., vol. 9), p. i80', pi. 23, figs. 27-29. (Not C. 



foulkei Lea.) 



Description. — The dimensions of a partially restored speci- 

 men, a plaster cast taken from a natural mould, are: length, 

 13.5 mm.; height, 8 mm.; thickness, 6.5 mm. Shell subcuneate 

 behind, full and rounded in front. Beaks small, incurved, situ- 

 ated back of the middle, pointing posteriorly. Antero-cardinal 



