679 Plat. 



sometimes continuous, at other times interrupted, then having 

 the appearance of very elongate pustules; at the base about 

 six in the space of 5 mm. No concentric strias have been ob- 

 served, though it is possible that they exist en more perfectly 

 preserved specimens. A typical specimen measures as follows: 

 Width at the base 30 mm.; thickness 20 mm.; height SO mm. ; 

 width of sides equal; width of ridges on posterior side 3 mm. ; 

 of depressions slightly more ; of carina 3 mm. This form re- 

 sembles the two specimens which are figured in the Pal. of 

 New York, Vol. V, Pt. II, PL 1, Figs. 20-23, which differ ma- 

 terially from the other figured specimens placed under that 

 species. The other specimens, though perfectly preserved 

 and showing concentric strias, have no indication of radiating 

 striae, while in the specimens described they are one of the 

 most characteristic features; they are also shown in the figures 

 mentioned above. The plications are also stronger and the 

 form more regularly conical. This species resembles P. stria- 

 tum irom this formation, but may be easily distinguished by 

 its straight form, the equal length of the sides, the coarser 

 striations, and the strong plications of the posterior sides ; from 

 P.lreve it is distinguished by its more elongate form, oval 

 aperture, more continuous radiating strias, and the conspicuous 

 plications of the posterior side. — Four miles north-west of War- 

 ren, Warren county, Pennsylvania. Chemung upper heds. 

 VTIIg, 

 Platyceras ( Orthonyohia) subrectum, Hall, Geol. Fourth 



a.RL M-';;T:r^^ ^^:;y---^^^ 172,fig.3;12th 



:'r^^.'.-^ Annual Rt. N. 



ii, 1879, page 1, plate 1, figs. 1, small specimen with no shell at 

 all ; 2, concave (ventral) side of a larger flat one, showing little 

 twisting except at the point (apex) ; surface, concentric striae, 

 sometimes crowded into wrinkles; robuster and more tapering 

 than P, dentalium^ and not ridged lengthwise. Upper Held, 

 limestone near Buffalo, N. Y. VIII a, — In Pennsylvania, re- 

 ported by C. E. Hall in MS. report on Collections of 1876, from 

 Marcellus and Oenesee. VIII 5, e. 

 16 



