84 GEOLOGY OF THE EUKEKxV J)18TKICT. 



Spirifera (Usjuncta. Sauguiuolites rigidus. 



Spirifera engelmanni. Paracyclas occideutalis. 



Athyris angelica. Euomphalus (P.) laxus. 



Atrvija retifularis. Euomphalus, sp.? 



Rhynchouella piiguus. Platyschisma ? ambigua. 



Rhyiichonella (L.) laura. Naticopsis, sp.! 



Ehyncbonella (L.) nevadensis. Styliola flssurella. 



Rhynchonella (L.) sinuata. Cytoceras nevadensis. 



Grammysia minor. Orthoceras, sp.? 



It is immediately overlying the limestone holding this fauna that the 

 argillaceous, cherty beds occur which cany poorly preserved fragments of 

 plant remains and the single species. Disc/ma minuta. They probably 

 represent the great development of the White Pine shale found upon the 

 east slope of Newark Mountain, but they are not represented on the map, 

 as they are recognized only in a few localities lying between the Nevada 

 limestone and Diamond Peak quartzite. 



CARBONIFEROUS ROCKS. 



Although rocks of this period cover large areas and make up the 

 greater part of many mountain ridges in the Great Basin, few localities 

 offer better exposures of all the epochs into which they have been divided 

 than that portion of the Diamond Range which lies within the limits of the 

 Eureka survey. To the northeast and east of Eureka, Carboniferous rocks, 

 more especially the limestones, present a greater thickness of strata than is 

 shown here, but in most cases the single, narrow ridges fail to expose in anv 

 continuous section the entire series of rocks from base to summit. At 

 Eureka the Carboniferous rocks have been estimated to measure 9,300 feet 

 in thickness, which, however, does not represent the full development of 

 the Carboniferous period, the Upjjer Coal-measures, the to]) of the Paleozoic 

 system having suffered a very considerable amount of erosion. This upper 

 limestone is by no means as thick as that found elsewhere. 



The Carboniferous rocks have been subdivided into four epochs: First, 

 Diamond Peak quartzite; second. Lower Coal-measure limestone; third, 

 Weber conglomerate; fourth, Upper Coal-measure limestone. 



