150 Systematic Paleoxtoi-ogy — ^Iiddle Devoxiax 



McCoys Ferry; Ernstvillc; in run at Hancock east of Catholic church; 

 along Flintstone Creek in Gilpin; west of Lock No. 56 at Great Caca- 

 pon ; ^ mile north of Green Spring Furnace; B. &. 0. E. R. cut at Han- 

 cock Station, W. Va. 



Collections. — Maryland Geological Survey; New York State Museum; 

 American Museum of Natural History. 



Chonetes scitulus Hall 

 Plate XII, Figs. 1-8 



Chonetes scitula Hall, 1857, Tenth Rep. N. Y. State Cab. Nat. Hist., p. 147. 

 Chonetes scitula Hall, 1867. Pal. N. Y., vol. iv, pp. 130, 141, pi. xxi, fig. 4; 



pi. xxii, figs. 6-11. 

 Chonetes scitula Hall and Clarke, 1892, Pal. N. Y., vol. viii, pt. i, pi. xvi, 



figs. 3, 4, 27, 32, 40, 44. 

 Chonetes scitulus Schuchert, 1897, Bull. U. S. Geol. Surv., No. 87, p. 178. 

 Chonetes scitulus Clarke, 1903, N. Y. State Mus., Bull. 65, p. 212. 

 Chonetes scitulus Grabau and Shimer, 1907, N. Am. Index Fossils, vol. ii, p. 



237, figs. 289a, b. 



Description. — Shell semioval ; hinge-line often not quite equaling the 

 greatest width of the shell. Ventral valve moderately gibbous in the 

 middle and regularly curving to the front and lateral margins; the gib- 

 bous portions narrowing towards the hinge-line, and the umbo little 

 elevated; abruptly depressed towards the cardinal angles, which are 

 nearly flat; cardinal area narrow and wider in the middle; delthyrium 

 partially closed by a convex deltidium and the aperture filled by the 

 cardinal process of the opposite valve ; margin provided with from 12 to 

 14 spines; the interior shows a slender median ridge and two strong 

 dental lamellae. Dorsal valve with a concavity less than the convexity 

 of the opposite valve; cardinal angles flat; cardinal area linear, half as 

 wide as that of tiie opposite vahe; the interior is strongly pustulose, with 

 a somewhat broad depression along the center, in the middle of wliich 

 there is a slender mesial ridge. Surface marked by fine subequal striae 

 which are sometimes sharp and angular, sometimes rounded and often 

 alternate in size toward the margin ; of these 15 to 20 may be counted 

 near the beak, while from bifurcation and intercalation there are from 



