FOSSILS OF THE CAMBRIAN. 27 
Dimensions of cephalic shield—Length, 3.25™"; width, 3.75""; caudal 
shield as 4 is to 5 in length and breadth respectively. 
A comparison of specimens made after the manuscript of this report 
was written shows that the supposed new species of Agnostus is identical 
with Mr. Meek’s A. bidens from the Gallatin River, Montana, also that 
Ptychoparia Gallatinensis occurs in association with it in Montana and 
Nevada. 
Formation and localities.—Cambrian. Prospect Mountain Group ; 
ranges from the upper portion of the massive Prospect Mountain lime- 
stone as found in the 700-foot level of the Richmond mine at Ruby Hill 
and on the east slope of Prospect Mountain, to the summit of the Ham- 
burg limestone, near the Hamburg mine, and into the base of the Po- 
gonip Group, occurring most abundantly in the upper beds of the Secret 
Canon shale, Eureka District, Nevada. Also in the Lower Pogonip Group 
on Pogonip Ridge, White Pine District, Nevada. 
Agnostus communis H. & W. 
Agnostus communis Hall & Whitfield, 1877. Geol. Expl. Fortieth Parallel, vol. iv, 
p. 228, pl. i, figs. 28 and 29. 
This species has a vertical range similar to the preceding, and occurs 
at: the same localities, although rarely in the same layer of rock. The orig- 
inal specimens were collected by the geologists of the Fortieth Parallel 
Survey from the White Pine Mining District, Nevada. 
Agnostus Neon H. & W. 
Agnostus Neon Hail & Whitfield, 1877. Geol. Expl. Fortieth Parallel, vol. iv, p. 229, 
pl. i, figs. 26, 27. 
Associated with Agnostus communis, and having essentially the same 
range and distribution in the district, the original types coming from the 
Kureka District, Nevada, by the same survey. 
