13 The Fauna of the Keyser Member oe the 



from any of these younger forms, however, in its much larger facet of at- 

 tachment upon the umbo of the pedicle valve." Weller, 1903. 



Most of the individuals referred to this species do not show the strong 

 wrinkles observed in the individuals from New Jersey while the area is 

 higher at times. They also attain a larger size, a large individual being 

 27 mm. long and 31 mm. wide, convexity of brachial valve 10 mm. 



Occurrence. — Helderberg Formatiox, Keyser Member. Keyser, 

 West Virginia ; Pinto, Devil's Backbone, Market Street Bridge Cumber- 

 land, Cookerly, Cash Valley, 1^ miles east of Bush, Maryland. 



Collection. — Maryland Geological Survey. 



SCHUCHERTELLA DEFORMIS (Hall) 



Plate LXT, Figs. 1, 2 



Orthis deformis Hall, 1857, Tenth Rept. N. Y. State Cab. Nat. Hist., p. 44. 

 Orthis deformis Hall, 1859, Pal. N. Y., vol. iii, p. 174, pi. xa, fig. 13; pi. xv, 



fig. 3, 1861. 

 OrtJiothetes deformis Schuchert, 1897, Bull. U. S. Geol. Survey, No. 87, pp. 



296-297. 



Description.—" Shell suborbicular, lenticular. A-^entral valve more 

 convex than the opposite, most elevated between the center and beak : beak 

 straight, or often distorted in consequence of having been the point by 

 which the shell was attached. Dorsal valve depressed convex, most ele- 

 vated near the beak : beak not extending beyond the hinge-line. Hinge- 

 line straight, equalling about three-fourths the width of the shell. Area 

 broad, flat, sometimes nearly on a plane with the axis of the shell. Fora- 

 men closed above, and filled below by the strong cardinal process. Surface 

 marked by prominent rounded striae, which increase by implantation, and 

 are crossed at intervals by distinct subimbricating concentric lines of 

 growth. The striae are distinctly tubular, with openings at the more 

 conspicuous lines of growth. The fine concentric strise are often scarcely 

 visible in the silicified specimens.'" Hall, 1859. 



Length about -1 cm. ; A\i(]th about the same. 



Occurrence. — Helderberg Formatiox, Keyser JMember. Devil's 

 Backbone, Cash Valley. 



Collections. — Maryland Geological Survey, U. S. National Museum. 



