LAMELLIBRANCHIATA FEOM THE EOOEXE MARLS. 235 



with the same features on the specimens from Claiborne, Ala., so far as a 

 cast can be said to agree with the external shell. The regular curvature 

 of the anterior, basal, and posterior margins, which blend into each other 

 without perceptible angulation, is also a marked feature, and one not 

 observed in any other American species. So that I feel no hesitation in 

 considering it as identical with the Claiborne examples. 



Formation and locality. — In the upper layers of the Upper Marls at 

 Shark River, New Jersey. 



Crassatella obliquata, n. sp. 

 Plate XXIX, Fig. 18, and PI. XXX, Figs. 13 aud 14. 



Shell, as known from internal casts, large and apparently of consider- 

 able thickness, especially in the cardinal ^wrtions, sometimes measur- 

 ing nearly three and a half inches in length by fully two and a half in 

 height. Valves moderately convex, although the casts generally show 

 evidence of considerable compression. Outline obliquely ovate, with very 

 broad and extended beak or rostral processes, which are broadly trianaular 

 in form and pointed obliquely upward and forward. Anterior end short 

 and narrow; posterior end broader and obliquely truncate, much longer in 

 the postero-basal region than above; basal margin strongly curved; mus- 

 cular scars large and moderately strong; pallial line usually distinct. 

 Surface of shell and hinge features unknown. 



This shell in its form, as shown by the casts, has differed from any 

 other species of the genus known in its large size, ventricose valves, and 

 oblique form combined. The beaks must have been very prominent, as 

 shown by the very large processes which have filled their cavities, much 

 larger, in fact, than in any other known species, while at the same time 

 they have had a very considerable breadth. Its general features are so dis- 

 tinctive that when found presenting anything like its normal form it can 

 scarcel}^ be confounded with any other species. But most of them have 

 suffered distortion in the marls to so great an extent as to almost obliterate 

 their original shape. 



A cast of a single valve, showing the imprint of the hinge-plate has 

 been obtained since the above description was written. The plate is 

 wider in proportion than that of C, alia Conrad, from the Claiborne, Ala., 



