478 a Kiag—Geohgy of the 4:0th Parall 



The Niagara furnishes the following : 

 Cladopora ap. (resembles C. seriata Hall). Atrypa reticularis . 

 Orthis (resembling 0. hybrida, Da?., but Atrypa resembles ^ 



Favosites Helderbergia Hall. Strophodonta punctulifera Can. f frag- 



Diphyphyllum, n. ap. ? ments only. 



Campophyllum (impressions only). Spirifera Vanuxemi ffall. 



r Bryozoans, t^ 



Trematospira 



young of 0. ob- Pentamerus galeatus Dal (frag. only). 



lata^aB).* ' Cryptonella, sp. ? (fragments only). 



Directly overlying the Ute limestone is a quartzite which is 

 distinctly developed in the Wahsatch Mountains, varying from 

 1,000 to 1,600 feet thick. It is usually white or pale green, 

 very finegrained and slightly schistose toward the top, and con- 

 tains occasional zones of conglomerate consisting of remarka- 

 bly smooth quartz pebbles in a fine siliceous matrix. From its 

 characteristic development in Ogden canon we have called it 

 the Ogden quartzite. It is again met with in western Nevada, 

 where it has a thickness of 700 or 800 feet. This body of sili- 

 ceous material is sometimes altogether wanting, its place being 

 taken by limestone, the Ute and Wahsatch limestones forming 

 one continuous body, siliceous impurities marking the horizon 

 of the Ogden. In the Wahsatch the Ogden quartzite is overlaid 

 by a limestone of very great thickness, to which we have given 

 the name of the Wahsatch limestone, and whose lowermost 

 fossils in the Wahsatch are Upper Helderberg. In western 

 Nevada also the Ogden quartzite is seen between the upper and 

 lower Helderberg horizons. We have included it provisionally 

 within the Devonian age, considering it the probable equivalent 

 of the Schoharie and Cauda-galli grits. 



Next above the Ogden quartzite, as just mentioned, lies the 

 Wahsatch limestone, a body reaching 7,000 feet in thickness in 

 the Wahsatch and over 8,000 in middle Nevada. Although 

 varying slightly in the purity of the material and constantly m 

 its physical aspect, it is nevertheless a single limestone senes. 

 The lower 1,200 or 1,400 feet are embraced within the Devo- 

 nian, and characterized by fossils of the Upper Helderberg and 

 Chemung group, and in a single instance a group which would 

 seem to have the facies of both the Upper and Lower Helderberg. 

 If in the lowermost members there is a mingling of Silunan 

 forms, as may possibly hereafter be proven, it will then be neces- 

 sary to move the Silurian line higher, so as to include the Ogden 



