414 Systematic Paleontology 



Spirifeu perdewi n. sp. 

 Plate LXX, Figs. 11-13 



Description. — This large, massive, subquadraiigular Spirifer has a 

 width of 55 mm. ; and will probably be most often confounded with S. in- 

 termedins, since it has much of the general exterior aspect of the latter. 

 However, the subquadrate outlinr -nnd less convex valves should readily 

 distinguish it from that species. The only other subquadrate Oriskany 

 form is S. concinnoideus, but this has a far greater number of plications. 

 The surface detail is not preserved, but as the species strongly resembles 

 S. intermedins, it is assumed that the plications are crossed by nearly 

 obsolete lamella^ terminating in minute simple spines. 



Length about 4 cm. ; width about 5.25 cm. 



Occurrence. — Oriskany Formatiox, Eidgely Member. Knobly 

 Mountain near Cumberland, Marjdand ; north fork of the South Branch 

 of the Potomac Eiver, Pendleton County, West Virginia. 



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



Spirifeu tribuarius n. sp. 

 Plate LXX, Figs. 14-lG 



Description. — Shell small, biconvex, plicate, with narrow cardinal areas. 

 Cardinal angles more or less strongly rounded so that some specimens are 

 transverse and others subrhomboidal in outline. Ventral valve most con- 

 vex, with a small, low, not strongly incurved cardinal area; median sinus 

 narrow, deep, and rounded, bounded by high and rounded or subangular 

 plications, on each side of which are from two to three smaller ones. 

 Dorsal valve convex, with a narrow median flattened fold, on each side of 

 which are deep, narrow depressions, and outside of these are from two to 

 four plications like those of the other valve. Ventral teeth strong and 

 unsupported by dental lamellge. Surface with many concentric, nearly 

 obsolete lamella bearing very delicate spines. 



Length about 10 mm. ; width 15 mm. 



This species may have developed from S. paucicostatus by adding a few 

 lateral plications and attaining larger size. The specific name is intended 



