FOSSILS OF THE CARBONIFEROUS. 233 
In outline this species is not dissimilar from Pterinopecten (Pecten) 
papyraceus, as illustrated by De Koninck (Anm. Foss., plate v, figs. 6, 6 a, b). 
It differs widely in surface characters. I know of no American species 
with which to compare it. 
Formation and locality—Lower portion of the Carboniferous Group, on 
the east slope of a small conical hill on the east side of Secret-cafion-road 
Cation, Eureka District, Nevada. 
Pterinopecten Spio, n. sp. 
Plate viii, figs. 1, la. 
Outline, including the ears, broadly truncato-ovate. Left valve de- 
pressed convex. Hinge-line nearly as long as the greatest width of the 
shell below. Anterior ear small, separated more sharply from the body 
of the shell than is usual in the genus; sinus rounded; posterior ear large 
and not very distinctly separated from the body of the shell. Beak small, 
abruptly pointed, and situated nearly on the anterior third of the length of 
the hinge-line. 
Surface marked by about 20 linear, radiating coste, with inter-spaces 
greater than the width of the cost, in which faintly-defined cost are 
sometimes shown; concentric lines of growth occur, and under peculiar 
conditions of preservation, as shown in fig. 1 of plate viii, form a reticu- 
lated structure with the radiating coste. 
Dimensions : height of an average specimen, 15"; width, 18""; con- 
vexity of left valve, 2™™ to 3™™. 
In outline and the form of the wings this species approaches that of 
Pterinopecten eafoliatus Hall, of the Devonian of New York (Pal. N. Y,, vol. 
v, pt. 1, p. 61, 1884), more nearly than to any other species known to me. 
Formation and locality—Lower portion of Lower Carboniferous lime- 
stone in cation directly south of a small conical hill on east side of Secret- 
cafion-road Cation, Eureka District, Nevada. 
