524 CRETACEOUS PALEONTOLOGY. 



Genus Corimya Agassiz. 



Corimya tenuis Wbitfleld. 



Plate LVIL, Figs. 16-18. 



1886. Corimya tenuis Whitf., Pal. N. J., vol. i (Monog. U. S. 

 G. S., vol. 9), p. 170, pi. 23, figs. 9-1 1. 



Description.— The dimensions of a nearly perfect internal 

 cast are: length, 32.5 mm.; height, 22 mm.; thickness, 10 mm.; 

 the length of the largest specimen observed is 37 mm. Shell sub- 

 elliptical to broadly triangularly ovate in outline; the valves un- 

 equally depressed convex, the right valve flatter than the left. 

 Beaks small, little elevated above the hinge-line, nearly central in 

 position. Anterior and posterior cardinal margins sloping away 

 from the beak in a broadly obtuse angle; anterior and posterior 

 margins rounded, the anterior higher than the posterior; basal 

 margin broadly convex. Surface of the casts marked by more 

 or less indistinct and irregular concentric undulations, and in 

 some specimens by faint radiating ribs on the anterior slope of 

 the shell. In the central portion of the casts, beneath the beak 

 and extending further posteriorly than anteriorly, wavy vascu- 

 lar impressions can often be seen extending about half way to 

 the ventral margin of the shell. Muscular impressions of mod- 

 erate size, the posterior ones more conspicuous than the anterior, 

 and bordered in front by a rather deep groove in the casts ex- 

 tending obliquely backward from behind the beak towards the 

 posterior margin. 



Remarks. — This species can be easily recognized by the un- 

 equal convexity of the valves which give to the .specimens a 

 slightly bent form, and by the conspicuous oblique furrow in 

 front of the posterior muscular scars in the casts, which in the 

 interior of the shells themselves was a ridge-like thickening, of 

 the valve. The species has only been observed in the form of 

 internal casts and the external surface markings are not known. 



Formation and locality. — Marshalltown clay-marl, Marshall- 

 town (Whitfield); Navesink marl, Atlantic Highlands (108), 

 near Crawfords Corner (126''), Crosswicks Creek (195), Mul- 

 lica Hill (169), Upper Freehold (Whitfield). 



Geographic distribution.- — New Jersey. 



