FOSSILS OF THE CARBONIFEROUS. Zig, 
upper lateral slopes of the valve; area beneath the beak unknown, as it is 
concealed by the adhering matrix. Dorgal valve nearly as convex as the 
ventral ; beak small, incurved, and projecting a little over the hinge margin; 
mesial lobe elevated, about as broad as the sinus of the opposite valve and 
with a slight median groove; lateral ribs, four on each side. 
Surface of valves marked by fine concentric lines of growth. 
This species is allied to S. Leidyi, but differs in the less number of ribs 
on the valves, and also in the rounded lateral angles. 
Formation and locality.—Lower portion of the Carboniferous Group, 
Richmond Mountain, Eureka District, Nevada. 
Spirifera neglecta Hall. 
Plate xviii, fig. 10. 
Spirifer neglectus Hall, 1858. Geol. Surv. Iowa, vol. i, pt. 2, p. 643, pl. xx, fig. 5. 
neglectus Worthen & Meek, 1875. Geol. Surv. Ilinois, vol. vi, p. 523, pl. xxx, 
figs. Le, 2a. 
This large and strongly-marked species of the Keokuk limestone of the 
Lower Carboniferous of Iowa and Illinois, is represented by single valves 
and one medium-sized entire shell. There appears to be a strong specific 
identity between the Nevada specimens and those from the Mississippi 
Valley. 
Formation and localities—Lower portion of the Carboniferous Group, 
Richmond Mountain, and on the east slope of a small conical hill on the 
east side of Secret-canon-road Canon, Eureka District, Nevada. 
Spirifera desiderata, un. sp. 
Plate vii, fig. 8. 
Dorsal valve subsemicircular in outline, extremities submucronate, 
moderately convex; mesial fold not very prominent and flattened across 
the top, well defined at the margins, and with a slightly depressed median 
line. 
Surface marked by about thirty simple rounded plications, which are of 
moderate strength and little elevated ; a few concentric lines are shown, but 
