596 CRETACEOUS PALEONTOLOGY. 



Remarks. — This species is only known from the internal casts. 

 It apparently resembled in its general form and markings, the 

 species described from the Shark River Eocene by Conrad as 

 Protocardia cwrta} ^ but it has more rounded outlines and is less 

 erect than that species. Both of these species were marked with 

 fine radiating ribs over the entire surface of the shell, and can. 

 therefore scarcely be included in the genus Protocardia. 



Formation^ and locality. — Hornerstown marl, near Juliustown. 

 (i6o); Vincentown sand, near Deal (122); Vincentown lime- 

 sand. New Egypt (143). 



Geographic distribution. — New Jersey. 



Genus ProTocardium Beyrich. 



Protocardium jerseyensis n. sp. 



Plate LXV.. Fig. 21. 



Description,. — Shell subglobular in form, small, the dimensions 

 of the type specimen being : height, 8 mm. ; width, 8.7 mm. ; con- 

 vexity of one -^alve, 3.5 mm. Valves obscurely subquadrangular 

 in outline, the anterior margin rounding from beneath the beaks 

 into the basal margin, ventral margin rounded, becoming a little 

 straighter posteriorly and curving rather abruptly into the nearly 

 vertically subtruncate posterior margin, post-dorsal margin nearlj 

 straight and horizontal near the beaks, bending regularly down- 

 ward into the posterior margin behind. Valves regularly and. 

 strongly convex, slightly flattened in the internal casts on the post- 

 umbonal slope. Beaks erect, nearly central in position. Surface 

 of the shell marked by very fine, regular, concentric, depressed 

 lines or grooves which become nearly or quite obsolete on -the 

 post-umbonal slope, alsoi by very fine, regular, radiating costae, 

 which are conspicuous upon the post-umbonal slope, becoming 

 obscure or entirely obsolete in front of the umbonal ridge. 



Remarks. — This species is characterized by its small size, the 

 specimen whose dimensions have been given being one of the 



' See Whitfield, Pal. N. J., vol. i (Monog. U. S. G. S., vol. i), p. 236, pi. 30r 

 figs. S-7. 



