MOLLUSCA. 557 



1864. Crassatella cuneata Meek, Check List Inv. Foss. N. A., 



Cret. and Jur., p. 11. 

 1886. Crassatella cuneata Whitf., Pal. N. J., vol. i, (Monog. 



U. S. G. S., vol. 9), p. 118, pi. 17, figs. 18-20. 



Description. — Shell small, the dimensions of a nearly complete 

 internal cast are: length, 16 mm.; height, 10.5. mm.; thickness, 

 6.5 mm. Subovate in outline, cuneata behind. Beaks erect, rather 

 prominent, situated about one-third the length of the shell from 

 the anterior extremity. Antero-cardinal margin sloping forward 

 from the beak ; anterior margin rounding into the basal margin ; 

 basal margin convex in front and straight or slightly concave 

 posteriorly ; posterior margin short, truncate ; post-cardinal mar- 

 gin long, sloping backward from the beak and meeting the pos- 

 terior margin at the extremity of the hinge-line in an obtuse angle. 

 An obtusely subangular umbonal ridge passes in a nearly straight 

 or slightly concave line from the beak to the postero-basal ex- 

 tremity ; the poBtero'-cardinal slope flat or slightly concave, the car- 

 dinal margin inflected. Surface of the shell marked with rather 

 strong, regular, concentric lines of growth. In well preserved in- 

 ternal casts the post-cardinal margin and the truncate posterior 

 margin are not sharply differentiated, the posterior extremity of 

 the shell being rather sharply rounded. The muscular scars 

 prominent in the casts. When the internal casts are well pre- 

 served to the margin of the shell, the free margins are finely 

 crenate. 



Remarks. — This is a small species and can usually be distin- 

 guished by its subcuneate posterior extremity. No specimens 

 preserved in such a manner as to exhibit the hinge-characters have 

 been observed, but there can be little or no question as to its 

 proper generic position. The species occurs most commonly in 

 the Merchantville clay-marl, and Whitfield's specimens from Mon- 

 mouth, probably meant for Monmouth County, doubtless came 

 from that horizon. 



Pormation and locality. — Merchantville clay-marl, near Ma- 

 tawan (loi), near Jamesburg (141), Lenola (163); Wenonah 

 sand, near Crawfords Corner (126^). 



Geographic distribution. — New Jersey. 



