214 PALEONTOLOGY OF NEW JERSEY. 



The shell differs in its general form and outline from any American 

 species hitherto described, but quite closely resembles G. pliimbea Desh., 

 from the Paris basin Eocene, but is rather more ventricose and somewhat 

 shorter. The internal cast differs from all American species in its trans- 

 verse form and broad posterior end. It most nearly resembles C. vadosa, 

 Morton, among- those from New Jersey, but is higher posteriorly; has 

 larger, broader, and more erect as well as more distant beak projections, 

 and the valves have been very much more ventricose. The shell appears 

 to be more thickened than is indicated in any of the other New Jersey 

 species 



Formation and locality. — The specimen preserving the shell, a rare case 

 in the marls, is from the base of the Upper Green Marls at New Egypt, and 

 the casts are from Squankum, New Jersey. The former is in the State col- 

 lection at Rutgers College, and the latter at Columbia College, New York. 



CARDIIDJE. 

 Genu.s CEIOCAEDIUM Conrad. 



Criocardium nucleolus, u. Bp. 

 Plate XXVIII, Figs. 10 and 11. 



Shell sviiall, less than half an inch in its greatest diameter, very ventri- 

 cose, obscurely quadrangular in outline, with nearly central, erect beaks, 

 which are moderately incurved and closely approximate. Hinge-line arcu- 

 ate; anterior and basal margins united in a single regular curve; posterior 

 end obliquely truncate, a little longer below than above. Surface of the 

 valves somewhat regularly curved from the subangular umbonal ridge to 

 the anterior margin; posterior slope narrow, but abrupt. Muscular im- 

 pressions distinct and proportionally large. Surface structure and hinge 

 characters unknown, as only casts are known, but the margin shows cren- 

 ulations indicating radiating Hbs. 



This species is peculiar among the New Jersey fossils for its small size 

 and rotund form, and I know no described species from other localities that 

 is sufficiently near it in character to be confounded with it. I am by no 



