402 Systematic Paleontology 



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. — Heldebberg Formation, Keysee Member. Devil's 

 Backbone, Cash Valley, Cumberland, Pinto, 1| miles northeast of Flint- 

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



Collection. — Maryland Geological Survey. 



[Maynard.] 



Spirifer paucicostatus n. sp. 

 Plate LXVIII, Figs. 30, 31 



Description. — Shell small, much like Amboccelia, but distinctly plicate. 

 Ventral valve strongly convex, with a small not well-developed cardinal 

 area; median sinus pronounced and bounded by two well-defined, de- 

 pressed, rounded plications outside of which are shallow grooves separating 

 them from the smooth lateral portions. Dorsal valve slightly concave with 

 a shallow but broad median sinus bounded by two low and rounded plica- 

 tions. Surface marked by concentric lines and varices of growth. There 

 may have been tubular spines, but the surface now appears to be smooth. 



The two pairs of dorsal adductor scars are clearly differentiated, narrow, 

 and extending to near the anterior edge of the valve. Cardinal process 

 and crural plates well developed. Dental plates of the ventral valve 

 prominent, thick, and restricted to the rostral region ; diductor scars very 

 narrow and long on each side, while the entire umbonal cavity is marked 

 by vascular sinuses. 



This little shell has the general expression of Amboccelia, with the 

 addition of two plications on each valve. It is, therefore, readily dis- 

 tingTiished from all associated species. Of its ancestors nothing is as yet 

 ascertained. Weller' has described from the Upper Oriskany of New 

 Jersey Metaplasia plicata that reminds one of S. paucicostatus. It may 

 prove that these are related shells, but the latter is readily distinguished 

 in having fewer plications. Common in the Shriver member. 



Occurrence. — Oriskany Formation, Shriver Member. Cash Valley, 

 Devil's Backbone, North Branch, Pinto, 21st Bridge. 



Collections. — Maryland Geological Survey, U. S. National I\Iuseum. 



^ GeoL Surv. N. J., Pal., vol. iii, 1903, p. 356, pi. xlvill, figs. 7-12. 



