FOSSILS OF THE POTSDAM GROUP. 217 



GlabelLi moderately tapering from the base anteriorly, and squarely 

 truncate in front, the width of the anterior end equal to half of the entire 

 height; marked by a single pair of transverse furrows near the base, which 

 are united and deepest on the middle of the glabella, the outer extremities 

 having a slightly forward curvature. The second pair of furrows are very 

 faintly marked, and sometimes obsolete or only seen in the reflection of 

 light across the surface, oblique, and situated anterior to the middle of the 

 length of the glabella; anterior furrows obsolete. 



Fixed cheeks rather narrow, prominent at the eye-lobes, and rapidly 

 sloping anteriorly and posteriorly; separated from the glabella by very 

 sharp and distinct dorsal furrows. Frgntal limb short, abruptly convex 

 between the anterior margin and the glabella, strongly arched upward in 

 the middle, and bordered by a narrow, thickened, rounded rim; oculnr 

 ridges not observable; occipital furrows and ring distinct. Lateral limbs 

 not observed. 



A pygidium associated in the same block is transversely broad, semi- 

 circular, or short paraboloid; nearly twice as wide as long, and margined 

 on the under side of the posterior border by a wide, considerably thickened, 

 recurved selvage. x\xial lobe narrow, depressed-convex, and marked by 

 six annulations exclusive of the terminal ones; lateral lobes depressed-con- 

 vex; their anterior margin bordered by an elevated ridge, which extends 

 with increasing strength to near the outer angle; two other faint ribs can 

 be detected on each lobe. 



The species somewhat closely resembles ConocephaUtcs Slmmardi Hall 

 (IGth Rept. State Cab., p. 154, pi. 7, figs. 1 and 2, and pi. 8, fig. 32). It is, 

 however, proportionally wider in front between the suture-lines, the palpe- 

 bral lobes are smaller, and the furrows of the glabella less distinct. The 

 pygidium is also very similar, but proportionally longer, the axis stronger, 

 and the ribs of the lateral lobes much more distinct. 



Formation and locaUty.—ln limestone of the Potsdam group, at Eureka, 

 Nevada. Collected by J. E. Clayton, esq. 



