FOSSILS OF THE DEVONIAN. 



157 



Formation and locality. Devonian limestone; associated with R. dupli- 

 cata and R. (L.) Laura. The Gate, northwest of Eureka, Eureka District, 

 Nevada. 



Rhyiichouella Emmonsi U. & W. 



Rhynclionella Emmonti Hall & Whitfield, 1877. Geol. Expl. Fortieth Par., vol. iv, p. 247, 



pi. iii, figs. 4-8. 



intermedia Barris, 1878. Proc. Davenport Acad. Nat. Sci., vol. ii, p. 285, 

 pi. xi, figs. 5-6. 



With the type of Rhynchonella Emmonsi before me, and a typical speci- 

 men of Rhynchonella intermedia, received from Rev. W. H. Barris, to compare 

 with it, I fail to observe any specific differences between them. The slight 

 differences mentioned by the author of R. intermedia would not serve to 

 separate the two shells, if found in the same stratum of rock, and the range 

 of variation in most species of the genus Ehynchonella is far greater than 

 between the two shells under consideration. R. Emmomi is a rare form in 

 the Upper Devonian of the White Pine District, Nevada, and Rev. Mr. Barris 

 writes me that it is also rarely met with in the Upper Devonian of Iowa. 



There is little doubt but that Rhynchonella intermedia, R. Emmonsi, and 

 R. venustula Hall are varieties of R. cuboides of the Devonian of Europe, 

 and when the opportunity offers to illustrate a series of specimens I think 

 this can readily be shown. 



/ 



Many American species now under local names will ultimately be 

 placed with species described from Europe, and the reverse will also be true 

 when American species have priority. Our knowledge of the widespread 

 geographic distribution of paleozoic species will be greatly increased with 

 better facilities for the comparison of specific forms from the great conti- 

 nental areas and islands. 



Subgenus LEIOBHYNCHUS Hall. 



Rhynchonella (Leiorhynchus) Nevadensis, n. sp. 

 Plate xiv, figs. 9, 9 a, 1>. 



Shell ovate or suborbicular, usually broader than long, or length and 

 breadth subequal; increases in rotundity with growth. 



Ventral valve in adult individuals gibbous above, curving uniformly 



