12 PALEONTOLOGY OF THE EUREKA DISTRICT. 
formed of spicule smaller than those preceding it, their rays all lying 
regularly disposed in two directions at right angle to each other, and so 
building up a net-work with square meshes. 
The skeleton is not preserved in any of the Nevada specimens, the 
different sized spicule lying scattered on the surface of the limestone shale 
or crowded together without any regularity to the direction of the rays or 
the size of the spicule. The spicule, however, appear to be identical in 
all respects with those described by Messrs. Salter, Hicks, and Sollas, and 
if they had not been scattered or crowded together by accident would 
form a skeleton similar to that described by Mr. Sollas. The under side of 
the spicule show no trace of a fifth ray or its point of attachment, appearing 
in this respect like the upper side, except that the surtace is a little concave 
instead of convex as on the upper side. They are silicious, and differ in 
mineral character from the spicule from the Cambrian rocks of Wales 
which have been replaced by pyrite. 
Dr. Hicks states that P. fenestrata occurs in the Longmynd Group, 
in the Menevian Group, and also in the Upper Lingula flags to the base of 
the Tremadoc rocks, giving a vertical range of from 8,000 to 10,000 
feet (Quart. Jour. Geol. Soc. London, vol. xviii, p. 181. 1872). It also 
occurs in black shales of Cambrian age in Norway and Sweden. 
Formation and localities Cambrian, Prospect Mountain Group. In 
the mountain shale near the Eldorado mine, and in the Secret Caton shale 
on the east side of Secret Cation, Eureka District, Nevada. 
BRACHIOPODA. 
Genus LINGULEPIS Hall. 
Lingulepis Mera H. & W. 
Lingulepis Mera Hall & Whitfield, 1877. Geol. Expl. Fortieth Parallel, vol. iv, p. 
206, pl. i, figs. 5-7. 
The specimens referred to this species are specifically identical with 
the types collected by the geologists of the Fortieth Parallel Survey in the 
Eureka District. 
