24 PALEONTOLOGY OF THE EUREKA DISTRICT. 
There appears to be very little difference between the Eureka speci- 
mens and those described by Professor Hall from the Potsdam sandstone 
of Wisconsin. Dr. C. A. White describes similar forms from Pioche, Nevada, 
where they occur in strata of (“Primordial”) Cambrian age. | 
Formation and localities —Cambrian. Prospect Mountain Group, in 
the upper beds of the Secret Canon shale, on the east side of New York 
and Secret Canons, and on the east side of the canon at the eastern side of 
Ruby Hill. Also in an outcrop of limestone on the west side of the foot- 
hills of Combs’ Peak, Antelope Valley, Eureka District, Nevada. 
PCECILOPODA. 
Genus AGNOSTUS Brongniart. 
Agnostus Richmondensis, n. sp. 
Plate ix, fig. 10. 
Cephalic shield moderately convex, length and breadth equal, sides 
scarcely parallel, rounding in front into the broadly rounded anterior 
margin. Glabella three-fourths the length and a little more than one-third 
as wide at the base as the width of the shield, it is elongate-conical in out- 
line, strongly defined by the dorsal furrows, and with the anterior third 
separated by a distinct transverse furrow, a little less than midway between 
this furrow and the posterior margin a short furrow penetrates from each 
side towards the base of a minute tubercle situated on the median line, 
two oblique furrows cut off the posterior lateral angles as two small rounded, 
triangular nodes; lateral lobes more convex than the glabella, divided 
anteriorly by a slight median furrow, surrounded by a narrow, rim-like 
margin, and ornamented by slightly irregular depressed lines that indent 
the surface from the margin nearly to the edge of the strong dorsal furrows. 
Surface smooth under an ordinary magnifying power. 
Dimensions.—Length and breadth, 2.5"; depth of shield, 0.75™™. Tho- 
racic segments and caudal shield unknown. 
