LAMELLIBRANOHIATA OF THE LOWER MARLS. 51 



attained the size common to that species, would have presented a very dif- 

 ferent appearance from that figured and presented by that species. The 

 larger of the two specimens seen has a height and breadth of very nearly 

 three-fourths of an inch. 



It seems difficult to place this species under the genus Syncydonema 

 Meek, on account of the large ears, which feature is in direct contradiction 

 of the features of that genus. Still Mr. Meek himself places Burlingtonensis 

 Gabb (Camptonedes Burlingtonensis of this work), with which it is possible 

 this may be identical, under it, notwithstanding this feature 



Formation and locality. — In the clay marls of the Lower Green Sand 

 at Haddonfield, N. J. From the collection of the Academy of Natural 

 Sciences, Philadelphia, labeled as above in Mr. Conrad's handwriting, but I 

 have not been able to trace the origin of the name or find any description 

 of the species. 



Genus AMUSIUM Klein. 



Amusium simplicum. 



Plate VII, Figs. 11 and 12. 



Peeten simplieus Conrad. J. A. i^r. S., Pbil., 2d series, Yol. lY, p. 283, PI. XLYI, Fig. 



44. Gabb, Synop. Gret. Ter., p. 160. Meek, Geol. Surv. K J., 1863, p. 725. 

 Sincijclonema ? simplieus (Con.). Meek, Check-list Smith. Inst., p. 7. Gabb, P. A. X. 



Sci., 1876, p. 319. 

 Pseudamusium simplica (Con.). Stoliczka, Pal. Indica, Yol. Ill, p. 420. 

 Sincyclonemaf simpUeia Conrad. A. M. Jour. Conch., Yol. Y, p. 99, PI. IX, Fig. 20. 



Shell small, barely half an inch in extreme height, and of equal width ; 

 discoid or very depressed convex, nearly or quite equilateral; margins of 

 the shell somewhat regularly rounded; hinge-line a little less than half the 

 width of the shell, and slightly rising from the center toward the extremi- 

 ties. Auriculations moderately large, the anterior side largest, slightly 

 rounded on the outer margin and forming a slight byssal notch at its junc- 

 tion with the body of the shell on the right valve. Cardinal slopes on the 

 right valve straight to near the point of greatest width of the valve, and 

 forming an angle of about fifty to fifty-five degrees with each other and 

 very strongly impressed. Beak small and pointed. On the left valve the 

 posterior ear is the smallest of the two, and the cardinal slopes less strongly 



