432 CRETACEOUS PALEONTOLOGY. 



at the extremity and only shallowly sinuate on the outer margin 

 between the hinge line and body of the shell. Anterior wing un- 

 known. Surface of the shell, on the left valve, strongly marked 

 by distant elevated radii, which seem to have been alternately 

 coarse and fine on the posterior half of the valve, judging from 

 the only cast examined, and equal in strength and moderately 

 curved forward on the anterior half; while the margin of the 

 valve seems to have been marked by strongly projecting points 

 corresponding to the ribs." (Whitfield.) 



Remarks. There is some question as to the occurrence of this 

 species in New Jersey. The specimen used by Whitfield is prob- 

 ably the type of the species which was said to have come from 

 Delaware by Morton in connection with his original description, 

 but according to Whitfield it is distinctly marked "N. J." in the 

 collection of the Philadelphia Academy. It has not been met 

 with in the recent collections of the Survey, and because of this, 

 and the uncertainty of its locality, it is not possible to determine 

 its horizon. It should probably be looked for, however, in the 

 horizon of the Merchant ville clay-marl, or perhaps in the Cliff- 

 wood clay. 



Formation and locality. Unknown. 



Geographic distribution. New Jersey ? 



Pteria navicula Whitfield. 

 Plate XLIL, Fig. 4. 



1886. Pteria navicula Whitf., Pal. N. J., vol. i (Monog. U. S. 



G. S., vol. 9), p. 70, pi. 14, fig. 8. 

 1905. Pteria navicula Johns., Proc. Acad. Nat. Sci. Phil. 



Description. "Shell of small size, the greatest length being 

 less than half an inch; very oblique and angularly ventricose, the 

 height scarcely more than half the length. Hinge line nearly as 

 long as the body of the shell, mucronate and slightly prolonged 

 at the posterior extremity, which is separated from the body of 

 the shell by a slight sinuosity. Anterior wing, if any, not pre- 

 served on the specimen; but the shell, although somewhat im- 



