FOSSILS OF THE CAMBRIAN. 



47 



swelling or boss that, but for the slight transverse dorsal furrow between it 

 and the glabella, might be mistaken for a continuation of the latter; the 

 eyelobes are comparatively large for a species of this character and occupy 

 a prominent position on the outer margin of the cheeks, a distinct ocular 

 ridge crossing the latter from the anterior margin of the eyes to the dorsal 

 furrow on a line with the front of the glabella; the lateral limbs are narrow, 

 rather short, and , slope rapidly downward back of the eyelobes; frontal 

 limb broad at the center, narrowing in front of the fixed cheeks and bor- 

 dered anteriorly by a not very distinctly defined rounded margin. The 

 facial suture curves a little inward in front of the eye and appears to ter- 

 minate on the front line somewhat in advance of a line passing through the 

 center of the tubercle in front of the glabella ; behind the eye it extends 

 obliquely outward and backward to the posterior margin of the head, out- 

 lining an elongate triangular postero-lateral limb. 



Under a strong magnifying power the surface is seen to be finely gran- 

 ulose. 



Free cheeks, thorax, and pygidium unknown. 



Formation and locality. Cambrian. Mountain shale band of the Pros- 

 pect Mountain Group, on the east slope of Prospect Peak, Eureka District, 

 Nevada. 



Ptychoparia (?) Linnarssoni, n. sp. 

 Plate ix, figs. 18, 18 a. 



The glabella and fixed cheeks are the only portions of this interesting 

 species that have been identified. The glabella is small in proportion to 

 the area occupied by the cheeks and frontal limb; it is conical in form, 

 truncate in front, moderately convex, and marked by three pairs of very 

 short, slightly impressed glabellar furrows; the latter only observed on very 

 perfect specimens; occipital ring narrow, as also the shallow occipital fur- 

 row ; fixed cheeks broad, elevated, and projecting forward on to the frontal 

 limb considerably in advance of the front of the glabella, the included 

 space between their anterior portions being occupied by an elongate oval 

 boss th&t is separated from the glabella by a rather broad, shallow furrow; 

 the boss or tubercle extends to the rounded thick frontal rim, from which it 



