FOSSILS OF THE CAMBRIAN. 43 
union of the free cheeks with the fixed cheeks would give the head a semicir- 
cular, strongly convex form, with rounded postero-lateral angles. The 
pygidium occurring with the other parts is transversely elliptical, about 
one-third wider than long, and elevated on the median lobe; the frontal 
margin is broadly rounded, the lateral margins scarcely angular at the 
union of the frontal margin and the more sharply rounded posterior line; 
axial lobe elevated, convex, about one-half the length of the pygidium, and 
marked by six transverse rings, including the terminal one; lateral lobes 
broad, sloping rapidly away from the axial lobe and then spreading out in 
a broad, flattened border; their surface is marked by three broad anchy- 
losed segments, besides the narrow anterior articulating projection and the 
broad posterior termination. 
Surface of the head finely granulose, and the pygidium the same, with 
the exception of the irregular strize on the border, the latter are sub- 
parallel to the margin. 
This species in the general form of the head and pygidium resembles 
many species referred by Mr. Billings to his genus Bathyurus, but it is 
nearer Dicellocephalus, if we compare it with typical forms of the genus 
from the Potsdam sandstone of Wisconsin, and is referred to that genus 
provisionally. . 
Formation and localities.—Cambrian. Prospect Mountain Group. 
Summit of Hamburg shale, on the ridge north of the Dunderberg mine, 
and ina matrix of a similar character at the southeast base of Lookout 
Mountain, Sierra Caton, Eureka District, Nevada. 
Dicellocephalus Tole, n. sp. 
Plate x, fig. 19. 
Glabella subquadrate, length exclusive of the occipital ring equal to 
the width at the base; it narrows a trifle anteriorly, is transverse in front, 
and has its laterai angles rounded; surface gently convex, rounding down- 
ward in front, and marked by twapairs of rather strong, but not deeply 
impressed, furrows that extend obliquely inward well towards the median 
line. 
