FOSSILS OF THE CAMBRIAN. 



51 



Ptychoparia (Euloma ?) dissimilis, n. sp. 

 Plate ix, fig. 28. 



Glabella prominent, strongly convex, the anterior lobe curving- down- 

 ward and under to the frontal margin; length and width at the base equal; 

 marked by two pairs of glabellar furrows extending obliquely inward, the 

 posterior pair nearly cutting off the triangular-shaped posterior lobes ; occip- 

 ital ring broad at the center, narrowing laterally ; occipital furrows strongly 

 impressed, as are the dorsal furrows along the sides of the central and pos- 

 terior portions of the glabella; fixed cheeks very narrow; palpebral lobes 

 large, moderately elongate, slightly sinuous, with a strong groove within 

 the margin; frontal lobe a narrow rounded rim; postero-lateral limbs un- 

 known. 



This species is known only by the parts mentioned. It is allied to 

 Ptychoparia Eos Hall, and a somewhat similar form has been described as 

 Menocephalus Sedgwlcki Billings. They appear to form a small group of 

 the Conocephalidye, the limits of which have not been defined. The refer- 

 ence to the genus Menocephalus is of doubtful propriety, since, up to the 

 present time, the fragment referred to as the type by Owen has never again 

 been even generically or specifically recognized in all the great collections 

 from the Potsdam sandstone of the Wisconsin and Minnesota, and it appears 

 to be practically impossible to identify it. The two species referred to the 

 genus by Billings, Palaeozoic Fossils, vol. i, p. 407, and Geology of Canada, 

 p. 237, also appear to belong to two distinct genera. 



Formation and locality. Cambrian. Secret Canon shale of the Prospect 

 Mountain Group, New York Canon, Eureka District, Nevada. 



Ptychoparia occidentalis, n. sp. 

 Plate x, fig. 5. 



Head within the facial sutures, exclusive of the postero-lateral limbs, 

 quadrangular in form; glabella subconical, the sides slightly converging 

 towards the rounded front; surface uniformly convex and marked by three 

 pairs of moderately oblique glabellar furrows, the two posterior pairs of 



