32 The Fauna of the Keyser Member of the 



apex : beak slightly incurved. Dorsal valve most convex in the middle : 

 mesial elevation not prominent : beak rising little above the hinge-line, 

 slightly incurved ; hinge-line less than the width of the shell, rounded at 

 the extremities. Area triangular, faintly defined, somewhat arcuate. 

 Foramen narrow; a strong median septum dividing the muscular area, 

 and extending to the apex of the foramen. Surface having about four 

 rounded moderately prominent folds on each side of the mesial sinus and 

 elevation, which become obsolete towards the beaks ; concentrically marked 

 by fine, regular, closely arranged imbricating lamellose stride." Hall, 1859. 



Length 1.5 cm. ; width 2.2 cm. 



The species Weller describes as Spirifer octocostatus in the Coeymans of 

 New Jersey ' is not well preserved, and it is probable that he had another 

 form. 



At Cash Valley and the section If miles northeast of Fliutstone and at 

 Hyndman, Pennsylvania, there is a species which has been identified as 

 Sjnrifer octocostatus. It differs from the normal S. octocostatus in having 

 the folds more angular and more elevated and they diverge more rapidly 

 from the beak, with the sinus deeper. The beak is not so much incurved. 



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

 Backbone, Cash Valley, Cumberland, Pinto, If miles northeast of Flint- 

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



Collection. — Maryland Geological Survey. 



SriRIFER VANUXEMI Hall 



Plate LXVIJl, Figs. 32, 33 



Spirifer vanuxemi Hall, 1859, Nat. Hist. N. Y. Pal., vol. iii, p. 198, pi. viii, figs. 

 17-23, 1861. 



Description. — " Shell rhomboidal, moderately gibbous : extremities 

 rounded. Ventral valve the less convex, having the beak elevated and in- 

 curved. Area small. Surface marked by broad rounded or somewhat 

 flattened and sometimes undefined plications, of which there are from two 

 to four on each side of the mesial fold and sinus ; concentrically marked by 



* Geol. Survey N. J., Pal., vol. iii, 1903, p. 288, pi. xxx, figs. 5-S. 



