FOSSILS OF THE CARBONIFEROUS. 



235 



Genus PTYCHOPTERIA Hall. 



Ptychopteria protoforme, u. sp 

 Plate viii, tig. 5. 



Shell obliquely elongate, narrowing anteriorly; posterior ear broad 

 and straight, anterior ear short; beak anterior, obtusely rounded; hinge 

 line long, but not quite equaling the greatest width of the shell below. 



Surface marked by obscure lines of growth. 



Interior characters unknown. 



Dimensions: height, 12^ ; greatest breadth, 20 mm ; convexity of left 

 valve, 2 mm to 3 mm . 



The outline of this species is more nearly like that of Ptychopteria 

 Proto Hall (Pal. N. Y., vol. v, pt. 1, p. 129, 1884) than that of any other 

 species known to me. The ear is not as broad, and it also terminates in a 

 more acute angle with the hinge-line, in this respect resembling P. sinuosa 

 Hall (loc.cit. p. 130). 



Formation and locality. Lower portion of Lower Carboniferous lime- 

 stone on east slope of a small conical hill on the east side of Secret-canon- 

 road Caflon, Eureka District, Nevada. 



Genus PINNA Linnaeus. 



Pinna inexpectans, n. sp. 



Plate xix, fig. 11. 



Shell elongate, lanceolate, over four times longer than wide; section 

 elliptical, valves not very convex; ventral and dorsal margins straight or 

 slightly convex. The dorsal or cardinal margin is a little thickened and 

 with a well-defined rounded rim at the edge. 



Surface marked by strong ridges subparallel to the dorsal and ventral 

 margins; they are more or less flexuous, and while obsolete on the upper 

 portion of some examples, are present on the entire width of the shell in 

 others. A few obscure concentric lines, parallel to the posterior margin, 

 cross the radiating plications. 



