Helderherg Formation in Maryeaxd 33 



fiue closely arranged iiiidulating stria) and stronger imbricating lines of 

 growth, which are again crossed by still finer radiating striae; the lafter 

 visible only under a magnifier." Hall, 1859. 



The individuals referred to this species in Maryland differ somewhat 

 from the typical *S'. vanuxcuii of the Manlius of New York in their ex- 

 pression, although the differences hardly justify a distinct varietal name. 

 They appear to be confined to the Chonetes jerseyensis zone. 



Occurrence. — Helderberg Formation, Keyser Member. Devil's 

 Backbone beneath the Gypidula zone. Cash Valley, If miles northeast of 

 Flintstone, Eoundtop. 



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



Spirieer eriensis Grabau 

 Plate LXIX, Fig. 7 



Spirifer eriensis Grabau, 1900, Bull. Geol. Soc. Amer., vol. xi, pp. 366-367, pi. 

 xxi, figs. 2o-b. 



Description. — " Shell small, pedicle valve strongly convex, almost 

 ventricose, subrhomboidal in outline, with the beak much elevated and 

 gently incurved. Mesial sinus pronounced ; angular in the center, with the 

 sides nearly flat, gradually and uniformly increasing in width from the 

 beak forward. Sometimes it is slightly rounded in the bottom. It is pro- 

 longed at the front of the shell as a prominent rounded lip. On either side 

 of the sinus is a moderately strong, broadly rounded, but not very promi- 

 nent plication, in addition to which there are about three or four on either 

 side, which are fainter and progressively become narrower away from the 

 sinus. Interspaces narrow, having the form of a depressed line, the broad- 

 est next to the plication adjoining the sinus. Brachial valve almost semi- 

 circular, moderately convex, with a straight hinge-line, which is shorter 

 than the greatest width of the valve. Beak elevated above the hinge-line 

 and incurved. Fold distinctly defined by a sharp depressed line on either 

 side, but not elevated much above the general surface of the valve. It 

 gradually and uniformly widens forward, is broadly rounded on top, and 

 is occasionally marked by a slight central depression. Ribs almost obso- 

 lete, a faint depression outlining the first on either side of the fold in some 



