248 PALEONTOLOGY OF THE EUREKA DISTRICT. 
rounded, obtuse angle, and rounding up more rapidly anteriorly in the 
more abruptly curved end. 
Surface marked by concentric lines of growth, and in well-preserved 
examples fine concentric striz are visible. 
This species is readily distinguished by its rotund outline from the 
associated species. 
Formation and localities —Associated with the preceding, and also on 
the northeast slope of the canon north of Pinto Peak, Eureka District, 
Nevada. 
Sanguinolites simplex, n. sp. 
Plate xx, fig. 11. 
Shell rather above the average size, transverse, irregularly broad-ovate, 
beaks small, compressed, and situated on the anterior third of the shell; 
umbonal slope angular from the beak to the posterior basal angle; general 
surface of the valves moderately and regularly convex, except the postero- 
cardinal slope, which falls away more rapidly from the umbonal ridge; it is 
marked by a faint, central longitudinal ridge. The general outline is not 
very much unlike that of the preceding species, except in the more pointed 
extremities and the near approach of the umbonal ridge to the postero- 
cardinal margin. 
Surface marked by fine concentric strize, and a few stronger lines of 
growth. 
Formation and locality—Lower horizon of the Carboniferous Group, 
eastern slope of a small conical hill on the east side of Secret-canon-road 
Canon, Eureka District, Nevada. 
Sanguinolites Salteri, n. sp. 
Plate xx, fig. 12. 
Shell rather small, transversely elongate, nearly three times as long as 
high; cardinal and basal margins subparallel or slightly diverging on the 
posterior half of the shell; beak small, depressed, and situated near the 
anterior end, which is narrow, short, and abruptly rounded; basal margin 
