152 PALEONTOLOGY OF THE EUREKA DISTRICT. 
Genus RHYNCHONELLA Fischer. 
Rhynchonella Horsfordi Hall. 
Plate xiv, fig. 3; plate xv, fig. 6. 
Rhynchonella horsfordi Hall, 1860. Thirteenth Ann, Rep. N. Y. State Cab. Nat. Hist., 
p. 87. 
(Stenocisma) horsfordi Hall, 1867. Pal. N. Y., vol. iv, p. 339, pl. liv, figs. 
24-32, 
A comparison of the Nevada forms of this species with those of the 
same stage of development from New York prevents their specific separa- 
tion. But few specimens were found, and it is not an abundant shell in New 
York, although occurring in the Marcellus and Hamilton shales. 
Formation and locality—Devonian limestone, Atrypa Peak, Eureka 
District, Nevada. 
Rhynchonella Tethys Billings. 
Rhynchonella tethys Billings, 1860. Canadian Journal, vol. v, p. 270, figs. 20-22. 
(Stenocisma) tethys Hall, 1867. Pal. N. Y., vol. iv, p. 335, pl. liv, figs. 1-8. 
This species is very closely related to the preceding, and in making a 
comparison of the two species with the specimens from Nevada, it is difficult 
to recognize constant specific characters that distinguish them. Both species 
are represented in the collections by the extreme forms, and until a large 
number of well-preserved specimens are collected, it may be premature to 
propose to unite them in one species. 
Formation and localities—In the Lower Devonian horizon at Comb’s 
Peak, and at Lone Mountain, 18 miles northwest of Eureka, Nevada. 
Rhynchonella? occidens, n. sp. 
Plate xv, figs. 3, 3a, b. 
Shell small, suboval to globose; strongly plicated. Ventral valve 
slightly less convex than the dorsal. 
Ventral valve somewhat convex above, becoming depressed midway of 
its length, with a shallow sinus that extends down and curves beneath; sides 
uniformly convex to the margins. Beak somewhat elevated and curving 
