132 Systematic Paleontology — Middle Devonian 



Occurrence. — Eomney Formation, Onondaga Member. 1^ miles 

 soutli of Berkeley Springs, West Virginia. Hamilton Member. P^ast 

 bank of Evitts Creek below Wolfe Mill. 



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

 American Museum of Natural History. 



Genus PHOLIDOPS Hall 



PhOLTDOPS HAMILTON IAE Hall 



Plate IX, Fig. 8 



PJioHdops hamiltoniae Hall, 1860, Thirteenth Rep. N. Y. State Cab. Nat. Hist., 



p. 92. 

 Pholidops hamiltoniae Hall, 1867, Pal. N. Y., vol. iv, p. 32, pi. iii, figs. 6-9. 

 Pholidops hamiltoniae Hall and Clarke, 1892, Pal. N. Y., vol. viii, pt. i, p. 157, 



pi. iv I, flgs. 31-34. 

 Pholidops hamiltoniae Schuchert, 1897, Bull. U. S. Geol. Surv., No. 87, p. 306. 

 Pholidops hamiltoniae Clarke, 1903, N. Y. State Mus., Bull. 65, p. 283. 

 Pholidops hamiltoniae Grabau and Shimer, 1907, N. Am. Index Fossils, vol. 



ii, p. 209, fig. 245. 



Description. — Shell regularly and uniformly ovate, broader near the 

 posterior end ; apex eccentric, little elevated, and slightly inclining to the 

 posterior side. Substance of the shell thin, and flattened toward the 

 margins. Surface marked by line closely arranged lamellose striae and 

 when magnified, shows indications of minute interrupted radiating striae. 

 Interior smooth, e.xcept an ovate, somewhat auriculate, and sometimes 

 slightly bilobed prominence beneath the apex, which marks the muscular 

 impression. The casts of the interior show a comparatively largo muscular 

 impression, which is shield-shaped or subovate and somewhat auriculate, 

 or with a deeper impression on each side above the middle. 



The Maryland specimens are imperfectly preserved, and but few char- 

 acters are sliown. They are minute, and one valve is somewhat convex 

 witli a rather deep muscular impression at the apex with the surface of 

 the shell marked by lamellose concentric striae. One specimen apparently 

 shows fine radiating striae; the outline of the shell, however, does not 

 appear so ovate as that of P. hamiltoniae. The specimen -with strong 

 concentric lines is apparently nearly circular in outline and suggested a 



