1 OSSILS 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 (?) tumifroiis H. & W. 



Geol. Expl. Fortieth Par., vol. iv, 



Plate x, fig. 16. 



Chariocephalus tumifrons Hall & Whitfield, 1877. 

 p. 224, pi. 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 in a 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 

 Caflon 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 AGEAULOS Cord a. 



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 



