EGBERT'S PEAK. 565 



north 20° to 25° west, with a dip from 40° to 50° to the eastward, while 

 the southeast foot-hills indicate a strike of north 8° to 10° west, and a dip 

 of 18° to 24° to the eastward. 



Organic remains were obtained from several localities, from the upper 

 horizons on both the north and -south slopes, yielding forms which may 

 range from the upper members of the Quebec group to the Lower Helder- 

 bergof the Upper Silurian. It is one of the few localities in Nevada along 

 the line of the Fortieth Parallel Survey where Upper Silurian fossils have 

 been found. 



The list embraces the following : 



Cladopora, sp.?; resembles C. seriata. 



Orthis, sp. 1 ; resembles 0. hybrida. 



Atrypa reticularis. 



Atrypa, STp.l] resembles A. nodostriata. 



Mhynclionella, sp. ? 



lUcenus, sp. 1 



The lower beds were not examined, but it would seem highly probable 

 that they may be found to contain forms characteristic of both the Quebec 

 and Primordial horizons, as found at White Pine and Eureka. 



Overlying the Eobert's Peak limestone, along the extreme northeastern 

 foot-hills, occurs a dark-blue cherty quartzite, which, from its position and 

 habit, has been referred to the Ogden Quartzite. It occupies but a limited 

 area, being concealed both to the east and west by volcanic rocks, and 

 derives its chief interest as indicating the relationship between the Robert's 

 Peak limestone and the PiQon uplift. 



Volcanic activity has had much to do in producing the displaced and 

 shattered condition of the Robert's Peak beds, which, both to the east and 

 north, have been broken through and buried beneath large outflows of both 

 trachytes and rhyolites, but chiefly by basalts. These intrusive rocks fre- 

 quently extend from the highest ridges down the long slopes of the mount- 

 ain to the valleys below. Trachytes are found breaking through the Ogden 

 Quartzites, where they occur as a dark-gray, rough rock, carrying shat- 

 tered crystals of sanidin and some dark mica. The trachytes are overlaid 

 by basalts, which, to the north, are connected with the basaltic table 



