152 PALEONTOLOGY OF THE EUREKA DISTRICT. 



Genus BHYNCHONELLA Fischer. 

 Rhynchonella Horsfordi Hall. 

 Plate xiv, fig. 3 ; plate xv, fig. 6. 



Rhynchonella Jiorsfordi Hall, 1860. Thirteenth Ann. Rep. N. Y. State Cab. Nat. Hist, 



p. 87. 



(Stenocisma) horsfordi Hall, 1867. Pal. N. Y., vol. iv, p. 339, pi. 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. 



Ehynchonella tethys Billings, 1860. Canadian Journal, vol. v, p. 270, figs. 20-22. 



(Stenocisma) tethys Hall, 1867. Pal. N. Y., vol. iv, p. 335, pi. 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 f occidens, n. sp. 

 Plate xv, figs. 3, 3 a, ft. 



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 



