12 PALEONTOLOGY OF THE EUKEKA DISTRICT. 



formed of spiculse 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 spiculse 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 spiculse. The spiculse, 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 spiculse show no trace of a fifth ray or its point of attachment, appearing 

 in this respect like the upper side, except that the surface is a little concave 

 instead of convex as on the upper side. They are silicious, and differ in 

 mineral character from the spiculse 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 which have been replaced by pyrite.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 Caflon shale 

 on the east side of Secret Canon, Eureka District, Nevada. 



BRACHIOPODA. 

 Genus LINGULEPIS Hall. 



Lingulepis Maera PI. & W. 



Lingulepis Mcera Hall & Whitfield, 1877. Geol. Expl. Fortieth Parallel, vol. iv, p. 

 206, pi. 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. 



