ORISKANY FAUNA OF BECKAFT MOUNTAIIT 51 



developed, perhaps more so than is usual with the upper Oriskany 

 shell. 



It is difficult to find any differences between this shell, specially 

 in its smaller form and the Chonetes dawsoni Billings from the 

 Gaspe sandstones. Both forms are but slight departures from the normal 

 lai-ge expression of the shell depicted in the original illustration of 

 C. complanata. 



Between this species and the Chonostr. helderbergia Hall 

 and Clarke of the Helderbergian, there seems but little difference ex- 

 cept in the more uniform striation of the latter and its slighter con- 

 vexity, but in the Chonostr. reversa Whitfield, of the Onondaga 

 the differentials are the distinctly fasciculate striation, the elongate 

 rather than transverse form and the diminutive size. 



Anoplia nucleata Hall 



Hate 7, ng. 14 



1859. Leptaena ? nucleata Hall, Paleontology of New York. 3 : 419, pi. 94, 

 fig. 1 a-d 



1892. Anoplia nucleata Clarke, op. cit. p. 413 



For other figures see Paleontology (^ New York. v. 8, pt 1, pi. 15, 

 fig. 17,18 and pi. 20, fig. 14-17. 



This little species is far more abundant here than in the arenace- 

 ous Oriskany of New York. It occurs also in some abundance in 

 rocks referred to the Oriskany in Jones county, Illinois. 



Orthothetes becraftensis sp. nov, 



Plate 7, flg. 15-28 



Shell small, suborbicular or elongate in outline. Pedicle-valve 

 erect at the beak, umbonal region generally sloping directly or with 

 low convexity to the peripheral margins ; sometimes slightly depressed 

 about the umbo. Brachial valve depressed at and about the beak, 

 becoming convex over the median and anterior regions. 



• Surface of both valves covered with strong, rounded striae in- 

 creasing by implantation, new striae generally appearing in successive 

 cycles. The surface also bears exceedingly fine, concentric lines which 



