Ferrusainous Sand Formation. 29i 



"is 



ted. Mostly found attached, and varies from one to three inches in 

 length. Same as No. 1 of this Synopsis. Common in New Jersey. 

 P. pelagica. (S. G. M.) PI. V, fig. 2. Subovate, convex, with 

 twenty five or thirty narrow elevated ribs. An unattached shell. 

 Found with the preceding. Resembles P. duplicata, (Sowerby) an 

 oolitic fossil. 



PECTEN. 



P. craticula. (S. G. M.) Shell suborbicular, unequal, with about 

 ten large, elevated, convex, longitudinally sulcated ribs, and a much 

 smaller one interposed between each pair. New Jersey. Very rare. 



P. anatipes. (S. G. M.) PI. V, fig. 4. With four or five broad 

 convex ribs, longitudinally striated; at the sides large striae replace 

 the ribs. Rarely more than half an inch in diameter. From the 

 overlying limestone of Claiborne, Alabama. 



P. perplanus. (S. G. M.) PI. V, fig. 5. Depressed, with about 

 twenty simple costae, transversely striated. Diameter less than an 

 inch. Found with the preceding species. 



P. venustus. (S. G. M.) PI. V, fig. 7. Shell thin^ depressed, 

 about half an inch in diameter, with fifteen or twenty double costae ; 

 those on the lower valve delicately beaded. From New Jersey. 



GRYPHiEA. 



G. plicatella. (S. G. M.) PI. IX, fig. 4. A minute species 

 from the overlying limestone of Alabama. I defer further notice of 

 it in the hope of obtaining larger specimens. 



OSTREA. 



In addition to the O. falcata, so common in New Jersey, I am 

 now able to give the characters of the three following species, all from 

 the same beds : 



O. plumosa. (S. G. M.) Ovato -triangular ; lower valve convex, 

 crenated near the hinge; dorsum marked with delicate striae, radia- 

 ting with fasciculi from the beak to the margin. 



O. panda. (S. G. M.) Same as species No. 2 of this Synopsis, 

 where it is referred, with a question, to O. Cristagalli of Europe. 

 (Vide Vol. xviii, pi. 3, fig. 22.) 



O. urticosa. (S. G. M.) Discoidal, thin, with numerous spinous cos- 

 tae ; many individuals usually adhering together. From New Jersey. 



ANOMIA. 



A. argentaria. (S. G. M.) PI. V, fig. 10. Thin, round, with 

 numerous concentric striae. 



