24 PALEONTOLOGY OF NEW JERSEY. 



Shells obtained from New Jersey and known only by the upper valves, 

 small, scarcely exceeding half an inch in diameter, subcircular in outline, 

 usually very little longer than wide and broadest below the middle of the 

 length. Usually, however, somewhat irregular. Apex of the dorsal valve 

 rather elevated and obtusely pointed, situated at about one-fourth of the 

 whole diameter from the dorsal margin. Surface of the shell strongly 

 lamellose over the outer half of most specimens and often to near the 

 apex. In most cases, however, the apex and umbo are smooth and pol- 

 ished, except for the very fine radiating lines which are visible under a 

 glass over much of the surface under the lamellae, or show on the expan- 

 sions as wrinkles, most especially on the short side of the apex. The sub- 

 stance of the shell is thick and entirely corneous, and the muscular scars 

 on the inside usually well marked. 



Localities: I have received specimens only from near Shiloh and 

 Bridgeton, N. J , both from the collections at Rutgers College and from the 

 National Museum 



