52 PALEONTOLOGY OF THE EUREKA DISTRICT. 
which are more strongly impressed and reach two-thirds the distance to the 
median line, the anterior -pair are short and faintly defined; occipital furrow ~ 
distinct; occipital ring rounded and rather under the medium size; dorsal 
furrows well impressed on the sides and in front of the glabella; fixed 
cheeks of medium width, not very convex, and sloping away gradually in 
front and behind; ocular ridges well marked; frontal limb extended a little 
beyond the fixed cheeks, slightly convex, and bordered by a flattened rim 
that is two-thirds as wide as the width between it and the glabella; eye- 
lobes of medium size; postero-lateral limbs narrow, extended, with a 
strongly marked continuation of the occipital furrow just within their pos- 
terior margin. The facial suture cuts very obliquely across the frontal rim 
of the head and abruptly recurving inward at its interior margin passes 
slightly inward in a direct line to the eyelobe, back of which it is directed 
outward with a backward curve on the outer third of the lateral limb, to the 
posterior margin of the head, which it cuts at a distance from the dorsal furrow 
equal to the width of the base of the glabella. 
Surface of head finely granulose; striate on the frontal limb. 
In the general outline of the facial sutures this species might be referred 
to Dicellocephalus, but the glabella is of the true type of Ptychoparia, and 
the other parts are not incompatible with a reference to that genus. 
Formation and locality.—Cambrian. Prospect Mountain Group, at the 
base of the Secret Canon shale on the west side of Secret Canon, Eureka 
District, Nevada. 
Ptychoparia similis, n. sp. 
Plate x, fig. 10. 
The glabella and fixed cheeks form a subquadrangular outline, with the 
central portion, opposite the eyes, arching inward, the frontal and postero-lat- 
eral limbs terminating the angles; glabella broadly conical, sides straight, 
converging slightly anteriorly to the rounded frontal margin; surface strongly 
convex and broken by three pairs of furrows, the anterior of which are very 
faint, the middle pair somewhat stronger and the posterior still more so; all 
are deflected a little backward, the posterior pair strongly outlining the pos- 
terior lobes; occipital ring strong and full and separated by a deeply im- 
