580 CRETACEOUS PALEONTOLOGY. 



ribs grow regularly larger in passing from the anterior cardinal 

 extremity to the postero-basal angle, those upon the posterior 

 slope are notably thinner and more sharply angular than those 

 upon the central and anterior portion of the shell, and one, about 

 the second or third from the postero-cardinal extremity, is much 

 higher and more conspicuous than the others. 



Formation and locality. Wenonah sand, near Crawfords Cor- 

 ner (l26 3 ). 



Geographic distribution. New Jersey. 



Cardium whitfieldi n. sp. 

 Plate LXIV., Fig. 8. 



1886. Cardium eufaulensis Whitf., Pal. N. J., vol. i (Monog, 

 U. S. G. S., vol. 9), p. 132, pi. 20, fig. 17 (not figs. 

 18-19). (Not C. eufaulensis Conrad.) 



Description. The dimensions of an internal cast are: height, 

 58 mm.; width, 55 mm.; thickness, 38 mm. Shell subcircular 

 in outline ; hinge-line nearly straight ; anterior and basal margins 

 curving with a regular, slightly decreasing curvature from the 

 anterior hinge extremity to the postero-basal region; postero- 

 basal extremity a little more sharply rounded; posterior margin 

 convex, a little straighter than the anterior. Beaks, in the cast, 

 rather small, nearly erect, acute, incurved, but little elevated above 

 the hinge-line. Valves moderately convex, their greatest promi- 

 nence along an oblique line from the beak to the postero-basal 

 extremity, the umbonal prominence not at all angular; anterior 

 slope long and gently convex, becoming somewhat compressed 

 towards the cardinal extremity; posterior slope shorter and more 

 abrupt, compressed towards the cardinal extremity, but less so 

 than the anterior. Muscular impressions on the cast incon- 

 spicuous, the posterior one much the larger. Lateral hinge-teeth 

 large and strong, horizontal in position, the anterior and pos- 

 terior ones about equidistant from the beaks; cardinal hinge- 

 teeth moderately strong. Inner free margins of the valves 

 strongly crenate all around. Surface of the shell marked by 



