244 PALEONTOLOGY OF THE EUEEKA DISTRICT. 



Surface marked by concentric lines of growth and numerous fine 

 radiating costse closely arranged. 



Interior characters unknown. 



Dimensions: height, 6; width, 10 mm ; 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, pi. 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 CaSon, Eureka, District, Nevada. 



Genus GEAMMYSIA De Verneuil. 



Grammy sia Hannibalensis Shumard (Sp.). 

 Plate xx, fig. 4. 



Altorisma hannibalensis Shumard, 1855. Geol. Surv. Missouri, vol. i, pt. 2, p. 206, pi. 



C, fig. 19. 

 Qrammysia hannibalensis Hall, 1870. Prelim. Notice Lam. Shells, p.62. 



Hannibalensis Meek, 1875. Pal. Ohio, vol. ii, p. 300, pi. xvi, figs. 5a-c. 



Hannibalensis Hall, 1883. Pal. N. Y., vol. v, pt. 1, Plates and Explana- 

 tions, pi. Ixi, 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 Cafion, 

 Eureka District, Nevada. 



