244 PALEONTOLOGY OF THE EUREKA DISTRICT. 
Surface marked by concentric lines of growth and numerous fine 
radiating coste closely arranged. 
Interior characters unknown. 
Dimensions: height, 6"; width, 10"; convexity of left valve, 3". 
Right valve unknown. 
This litttle shell is allied to Macrodon parvus W. and W. (Proc. Boston 
Soc. Nat. Hist., vol. viii, p. 299, 1862) of the Burlington Group of Iowa, 
and M. Chemungensis Hall (Pal. N. Y., vol. v, pt. 1; Plates and Explana- 
tions, pl. li, figs. 11-16, 1883), from the Chemung Group of New York. 
It is distinguished from each by its short form and strongly ornamented 
surface. The generic reference is made on the general character of the ex- 
ternal shell, as the hinge-line and internal characters are unknown. 
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 Canon, Eureka, District, Nevada. 
Genus GRAMMYSIA De Verneuil. 
Grammysia Hannibalensis Shumard (Sp.). 
Plate xx, fig. 4. 
Allorisma hannibalensis Shumard, 1855. Geol. Surv. Missouri, vol. i, pt. 2, p. 206, pl. 
C, fig. 19. 
Grammysia hannibalensis Hall, 1870. Prelim. Notice Lam. Shells, p.62. 
Hannibalensis Meek, 1875. Pal. Ohio, vol. ii, p. 300, pl. xvi, figs. 5a—c. 
Hannibalensis Hall, 1883. Pal. N. Y., vol. v, pt. 1, Plates and Explana- 
tions, pl. 1xi, figs. 23-33. 
After comparing the Eureka examples of this species with authentic 
specimens from the Waverly sandstone of Ohio, no reasonable doubt re- 
mained of their specific identity. 
The species ranges from the Chemung Group of New York to the 
Waverly of Ohio, and at the base of the Carboniferous of Iowa and Mis- 
souri. 
Formation and locality.—Carboniferous Group, lower portion, on east 
slope of a small conical hill on the east side of Secret-canon-road Canon, 
Eureka District, Nevada. 
