20 The Fauxa of the Keyser Member of the 



Description,: — " Shell subtriangular, wider than long, the postero- 

 lateral margins sloping from the beak, where they form an angle of from 

 95°-115°, in nearly straight lines to a point a little posterior to the middle 

 of the shell; 1he lateral and front margins regularly rounded. The 

 pedicle valve usually a little less convex than the opposite one; its beak 

 prominent, arched, but not strongly incurved ; the sinus is rather abrupt, 

 not reaching quite to the beak. The surface of the brachial valve curves 

 gently to the margins, except toward the front, where the mesial fold is 

 rather abruptly elevated. The surface of each valve is marked by from 

 20-24 simple, angular plications, of which two or three, somewhat coarser 

 than the remainder, are depressed in the medial sinus, with a correspond- 

 ing number elevated in the fold of the brachial valve. 



"The dimensions of a rather large specimen are: Length lo mm.; 

 width 19.5 mm. ; thickness 10 mm. 



"This shell is a rather common one in the lower beds of the Decker 

 Ferry formation. It resembles Sienocliisrna foruiosa Hall, from the 

 higher portion of the Helderbergian series, but may be distinguished 

 from that species by its coarser plications, its greater proportional width 

 and by its less strongly convex valves, which gives to members of this 

 species a less thickness of shell." Weller, 1903. 



This species differs but little from S. formosa of which it may be con- 

 sidered a variety. 



Occurrence. — Heldekberg ForjMAtiox, Keyser Member. Cash Valley, 

 National Eoad east side of Warrior Mountain, Devil's Backbone, Corrigan- 

 ville, Maryland; Keyser, West Virginia; Hyndman, Pennsylvania. 



Collection. — Maryland Geological Survey. 



Genus CAMAROTCECHIA Hall and Clarke 

 CaMAROTOSCHIA (?) LAMELLATA (Hall) 



Plate LXIIL Figs. 9, 10 



Atrypa lamellata Hall, 1852, Nat. Hist. N. Y., Pal., vol. ii, p. 329, pi. Ixxiv, 



figs. llff-7i. 

 RhynchoneUa (?) lamellata Schuchert, 1897, Bull. U. S. Geol. Survey, No. 87, 



p. 359. 



Description. — " Subrhomboidal, the ventral valve more convex; beak 

 of the dorsal valve incurved, small, acute and prominent; surface marked 



