NORXriERN CORTEZ RANGE. G09 



berg fossils. The limestone is dark, fine-grained, and rather siliceous, tliinly 

 bedded, and interstratified Avith light-reddish siliceous shales, about one- 

 fourth inch in thickness, having some branching impressions like plant-roots. 

 The beds from which the fossils were obtained are a series of thin-bedded 

 limestones near the upper portion of the formation. The following species 

 were determined by Messrs. Hall and Whitfield : 



Atrypa reticularis. 



Pentamerus galeatus. 



Sfrophodonta, sp. (like S. pimctulifera). 



Orthis, sp. ? (allied to 0. varica). 



Trematosxnra. 



Ccelospira (new sp.). 



JRhjncJioneUa, sp. ? 



FavositeSj sp. '? (allied to F. Helderherrjia), 



DiphyphyUum (new sp.). 



Campophyllum^ sp. ? 



A thickness of 500 to 700 feet of limestones is here exposed. Their 

 general dip is to the eastward, the beds lying nearly horizontal at the west- 

 ern face of the hill, and steepening in dip to the eastward. It would appear 

 therefore as if this little body of limestone had been faulted up. The 

 quartzites, which, from their stratigraphical position and general litholog- 

 ical character, have been considered to represent the Ogden Quartzite, are 

 found along the eastern and southern flanks of the hill, conformably 

 overlying the limestones. They also crop on the western side of Boulder 

 Creek, at the foot of the bluffs formed by the flows of rhyolite and basalt 

 of the Shoshone Mesa. The immediate foot-hills of the Cortez Range, in 

 the neighborhood of Boulder Creek Valley, are covered by thick deposits 

 of Quaternary gravel and soil, so that the structural relations of the out- 

 crops of the Silurian with the Weber Quartzites of Dalton Peaks could not 

 be definitely established. 



From Dalton Peaks to Mount Neva, in the deeper ravines, are exposed 

 frequent outcrops of quartzites having a general north and south strike, and 

 the same lithological character with the Weber Quartzites of the Seetoya 

 39 D a 



