FOSSILS OF THE CAMBRIAN. 53 
pressed occipital furrow; dorsal furrows distinct at the front and sides of the 
elabella; fixed cheeks narrow and rising rapidly from the dorsal furrows to 
the palpebral lobes, sloping away somewhat abruptly to the front and back; 
frontal limb short and broad, convex, and sloping quite rapidly to the slight 
furrow within the broad, planulate margin, which appears to be a continua- 
tion of it; postero-lateral limbs narrow, posterior margins rather strong, 
with a narrow groove within. 
Surface of the glabella finely pustulose. 
This species is allied to P. Montanensis Whitfield, but differs in the 
character of the frontal limb very decidedly, as also in the planulate margin. 
Some of the examples show the front margin cut away by the suture line 
which crosses it obliquely from about one-third the distance from the center, 
at its front margin, to the postero-lateral angle. 
Formation and locality—Cambrian. Prospect Mountain Group, in the 
upper beds of the Secret Canon shale across the cation opposite the 
northeast dump of the Richmond mine shaft, Ruby Hill, Eureka District, 
Nevada. 
Ptychoparia similis, var. robustus, n. var. 
Plate i, figs. 9, 9a. 
Glabella and fixed cheeks subquadrangular in outline. Glabella ob- 
tusely conical, sides slightly converging to the rounded front; surface 
convex, marked by two pairs of rather short, slightly impressed, oblique 
furrows; occipital ring strong, with a well-defined occipital furrow; dorsal 
furrows well defined in front and at the sides of the glabella; fixed cheeks 
narrow, rising rather rapidly from the dorsal furrows up to the front of the 
small palpebral lobe and then arching over to unite with the short, rounded 
frontal limb ; ocular ridges well marked; frontal margin rather broad and 
flat; postero-lateral limbs narrow as in P. similis. Surface of the glabella 
and postero-lateral limbs finely pustulose. 
This species, in the parts preserved, is closely allied to P. similis. The 
glabella is shorter, more convex, and nearly as broad as long, while that of 
P. similis is one-fourth longer than broad. The entire appearance gives the 
idea of its being a robust form of P. similis. 
Formation and locality —Same as Ptychoparia similis. 
