72 PALEONTOLOGY OF THE EUREKA DISTRIOT. 
Genus ORTHIS Dalman. 
Orthis perveta Conrad. 
Plate xi, figs. 3, 3a, b. 
Orthis perveta Conrad, 1843. Proc. Acad. Nat. Sci. Phila., vol. i, p. 333. 
Hall, 1852. Pal. New York, vol. i, p. 120, pl. xxxii, figs. 5a-c. Ibid. 
Geology of Wisconsin, p. 42, figs. 7a—d, 1862. 
Billings, 1863. Geol. Canada, p. 130, figs. 57 a-f. 
This species is quite abundant in the upper beds of the Pogonip Group 
at Lone Mountain, and it also ranges through nearly 1,000 feet of the lime- 
stone of White Mountain, and is found at about the same horizon on the 
eastern slope of the ridge east of the Hamburg mine, as in the lower beds of 
White Mountain. . 
A direct comparison of the Nevada specimens with the types of the 
species in the American Museum collections show their specific identity, 
and also that similar variations occur in examples from the widely-separated_ 
localities. In Wisconsin it is found in the Trenton limestone, and in Canada 
Mr. Billings identified it from the Chazy limestone. 
A small but quite perfect specimen is illustrated. Owing to the partial 
exfoliation of the shell, the radiating strize are not as strong as on the unin- 
jured surface. 
In the expedition of 1882 this species was found in the upper part of 
the Pogonip Group, on Pogonip Ridge, White Pine District, Nevada. 
Orthis testudinaria, Dalman. 
Plate xi, figs. 10, 10a. 
Orthis testudinaria Dalman, 1827. Vet. Acad. Hand., Stockholm, p. 115. 
Orthis testudinaria Conrad, 1839. Emmons, 1842; Hall, 1852. Pal. N. Y., vol.i, p. 117, 
pl. 32, figs. La-l. Whitfield, Geol. of Wisconsin, vol. iv, p. 258, pl. xii, figs. 
By t, 1883, 
See Davidson’s Monograph British Silurian Brachiopoda. 
After comparing our specimens with those from New York, Ohio, and 
Wisconsin, we are unable to discover any differences of specific value be- 
tween them, although the eastern forms are from the Trenton Group=Tren- 
ton limestone and Hudson River formations, and the Eureka specimens 
