FOSSILS OF THE CAMBRIAN, 61 
them as specifically distinct. The frontal limb scarcely projects beyond the 
front line of the glabella, as it slopes abruptly downward, although it is 
represented as projecting out some distance in the specimen illustrated owing 
to a narrow seam of calcite crossing it and throwing it forward. 
Formation and locality—Cambrian. Prospect Mountain Group, eastern 
base of Lookout Mountain, Sierra Valley, Eureka District, Nevada. 
Genus CHARIOCEPHALUS Hall. 
Chariocephalus (?) tumifrons H. & W. 
Plate x, fig. 16. 
Chariocephalus tumifrons Hall & Whitfield, 1877. Geol. Expl. Fortieth Par., vol. iv, 
p. 224, pl. ii, figs. 38, 39. 
The types of this species came from the lower limestones of Pogonip 
Mountain, in the White Pine District, Nevada. : 
The specimen illustrated as the type of the species is the extreme form 
attained by the adult. Traced ina series of individuals, towards the younger 
form, the anterior lobe of the glabella is seen to lose its tumid, projecting 
character, and to curve down to the frontal margin and not overhang it, as 
in the older individuals. One of the intermediate phases of growth is shown 
by fig. 16, plate x. 
Formation and locality—Cambrian. In the upper beds of the Secret 
Cafion shale on the north side of the canon, opposite the dump of the shaft 
of the Richmond mine on Ruby Hill, Eureka District, Nevada. 
Genus AGRAULOS Corda. 
Agraulos ? globosus, n. sp. 
Plate ix, fig. 23. 
Glabella and fixed cheeks, exclusive of the postero-lateral limbs, sub- 
quadrate, strongly convex. Glabella with the sides and front rounded, 
convex, and with the surface apparently smooth; dorsal furrows well 
defined; occipital ring not perceptibly separated from the glabella; fixed 
cheeks of medium width; palpebral lobes small, the cheeks sloping down 
to them; frontal limb about one-third as long as the glabella, convex, with- 
out an apparent marginal rim, and with a slight furrow at the union with 
