FOSSILS OF THE CAMBRIAN. 



53 



pressed occipital furrow; dorsal furrows distinct at the front and sides of the 

 glabella; 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, plauulate 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 canon opposite the 

 northeast dump of the Richmond mine shaft, Ruby Hill, Eureka District, 

 Nevada. 



Ftychoparia similis, var. robustus, n. var. 

 Plate i, figa. 9, 9 a. 



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. 



