FOSSILS OF THE CARBONIFEROUS. 223 
Genus RHYNCHONELLA Fischer. 
Rhynchonella Eurekensis, n.§sp. 
Plate xviii, figs. 8, 8da-c. 
Shell below the average size; somewhat trigonal in outline; the width 
and height subequal, or the latter a little greater than the former; dorsal 
valve a trifle deeper than the ventral. 
Ventral valve with a prominent beak and strongly marked but not 
deep mesial sinus that is about one-half the width of the shell at the front 
margin; sides sloping gradually away from the edges of the sinus and more 
abruptly from the somewhat elevated upper portion. Dorsal valve much 
more convex than the ventral and marked by a slight, broad mesial fold on 
the lower portion; beak strongly incurved; general surface rounding to the 
margins from the central portions of the valve. 
Surface of the valves marked by from 40 to 50 round, simple plications. 
This species is distinguished from any described by its general form 
and the numerous radiating plications. 
Formation and localities—Lower portion of the Carboniferous Group, 
east slope of a small conical hill on the east side of Secret-canon-road 
Canon, and on the northeast side of the cation north of Pinto Peak, Eureka 
District, Nevada. 
Rhynchonella Thera, u. sp. 
Plate vii, figs. 6, 6a-c. 
Shell small, subglobose or suboval, strongly convex, with a prominent 
mesial elevation and suture. 
Ventral valve a little less convex than the dorsal, the greatest con- 
vexity being on the posterior half; below the middle a broad, not very 
sharply defined sinus begins, which becomes deeper and expands towards 
the front; beak imperforate and slightly curved over that of the opposite 
valve. 
Dorsal valve most convex at the middle; the median fold is not usu- 
ally strongly defined; it has a slight central sinus that reaches from near 
the beak out to the front termination of the fold, the latter starting about 
the center of the shell. Surface marked by fine concentric lines of growth. 
