80 GEOLOGY OF THE EUEEKA DISTRICT. 



Spirifera engelmanni and the two Chemung forms, Rliynchonella duplicate and 

 E. sinuata, both fcmnd at several localities in the Upper Nevada limestone. 

 Rescue Hill, on the east side of Rescue Canyon, is a faulted block of 

 Devonian limestone. Along the abrupt east slope of the hill the north and 

 south Rescue Canyon fault cuts off the limestone from that found on the 

 opposite side of the canyon, while an east and west fault, approximately 

 coinciding with the course of Silverado Canyon, intersects the Rescue Can- 

 yon fault, and separates the hill from the limestone body to the north. 

 The beds forming the summit of Rescue Hill belong to strata somewhat 

 higher in the series than those found on the summit of Sentinel Peak and 

 Island Mountain, but the lower limestones of the three localities may be 

 easily correlated. In a light bluish gray limestone just below the top of 

 Rescue Hill the following grouping of fossils occurs : 



Lingula ligea, var. iievadensis. Mytilarca chemungensis. 



Productus hallanus. Leptodesma transversa. 



Productus shumardianus. Nucula rescueusis. 



Productus stigmatus. Nucula (like N. niotica, Hall). 



Productus subaculeatus. Grammysia minor. 



Spirifera (M.) maia. Sanguinolites ventricosus. 



Atrypa reticularis. Paracyclas occidentalis. 



Rhynchonella castanea. Platyceras carinatus. 



Rhynchoiiella duplicata. Bellerophon pelops. 



Ehynchouella (L.) laura. Naticopsis, sp.f (like If. aequistriata, Meek). 



Rhynchonella iievadensis. Tentaculites gracilistriatus. 



Rhynchonella siuuatus. Styliola fissurella. 



Cryptonella piuonensis. Proetus haldermanni. 



The Rescue Canyon fault, as already described, is a profound displace- 

 ment. After crossing Silverado Canyon at the head of Rescue Canyon, it 

 extends northward until concealed beneath the great basalt flow. By 

 reference to the map (atlas sheets vm and x) the course of the fault will 

 be seen along the base of Sugar Loaf and Sentinel Peak. In the faulted 

 block to the eastward there occurs a wedge-shaped mass of Devonian 

 limestone lying north of Silverado Canyon and east of Island Mountain 

 and Sugar Loaf. It conformably underlies the great body of White Pine 

 shale and admirably shows the relation between the Nevada limestone 

 and the overlying shale. These beds directly underlying the shale are of 



