Ptycho. 



840 



immediately below the cardinal line ; separated from the body 

 by a narrow but conspicuous depression. Surface ornamented 

 by faint radiating striae which are obsolete except on perfectly 

 preserved specimens, and also by fine concentric striae, which 

 frequently become fasciculate on the anterior portion of the 

 shell. This species may be distinguished from any other at 

 present known by the slight obliqueness of the body of the 

 shell, the basal margin being nearly parallel with the hinge 

 line; the margin is decidedly convex; in nearly all other 

 species it is straight or concave ; the wing extends beyond the 

 body of the shell. The outline is very similar to that of some 

 forms of the genus Oypricardinia. Hill north of Warren, 

 Warren county, Pa. Chemung, VIII g. 



Ptychopteria proto, Hall, Pal. N. Y., Vol. V i, plate 23, 



'^' i^,.^- .^t-^^ ^^^' 1^' 14^ ^^^ l^f^ valves; 



■>:-.^ A^ li^^k found in the Upper Chemung. 



^\U ^^^F ^^^9H|k near Smethport,McKeanCo., 



u 1/ n /•/* ^JIH^P Pa. Also Randall's Warren 



HalLFaLVf^phl^, ^i^ specimen No. 9590. VIII g. 



Ptychopteria salamanca, Hall, Pal. N. Y. Vol. V i, 1884, 



HaiL Fed, NX Voi,Vi\im^ l^l^^^^^ _ 



page 131, pi. 23, fig. 17, 18, two left valves; 19 hinge view of 

 18, showing the relative convexity of the valves and compara- 

 tive elevation of the beaks; 20, right side of specimen with 

 both valves partly opened. Specimens various on account of 

 degrees of preservation ; often pressed out of shape ; weathered 

 ones often without strias, and concentric lamelle more promi- 

 nent. In a Chemung sandstone above the Salamanca conglom- 

 erate^ Salamanca, N. Y. In Penna. collections, specimen 882-1 

 VIII g. 



