UPPER PALEOZOIC (dEVONIC). 233 
the upper Devonian of Western New York. Including all that 
is now rated as above the Hamilton shales and below the Bed- 
ford shales this upper Devonian of Eastern Ohio is from 400 
to 2000 feet in thickness, thinning westward (see Professor Or- 
ion's Preliminary Report on Petroleum and Gas, 1887, p. 26). 
When we reach the central part of the interior area we find 
the Devonian represented by limestones running up into fine 
argillaceous shales, resting on upper Silurian limestones which 
in numerous places are of Niagara age, and in the southern 
border of the region are more or less siliceous, and hold fossils 
of the later Silurian time, as in the Delthyris shales of Missouri 
which are, doubtless, as late as Lower Helderberg time. This 
central area lacks the black shale and runs up immediately into 
Sub-carboniferous limestones, calcareous shales and sandstones, 
and the total representatives of the Devonian are scarcely 200 
feet thick. 
The Western Devonian Area. 
I take the Nevada section of the Eureka district as typical, 
since this has been carefully developed by the labors of Hague 
and Walcott (see Walcott's Monograph, Paleontology of the 
Eureka District, U. S. Geol. Survey, 1884). 
The peculiarities of this section are as follows t 
Lying unconforraably upon a thick series of limestone beds, 
representing the Trenton and, at the top, the Niagara series of 
eastern sections, comes the Nevada Limestone, <)000 feet thick, 
indistinctly bedded and siliceous below, and becoming massive 
toward the top with intercalated beds of shale and quartzite. 
The same fauna runs from bottom to top, but with some change 
in part of the species. In the lower 500 feet the fauna is dis- 
tinctly lower Devonian, and in the terminal 500 feet it is as dis- 
tinctly allied with the upper Devonian of the east. Throughout, 
there are found species which in the typical eastern sections are 
restricted to particular zones. In its species it shows closer rela- 
tionship with the Iowa Devonian than with the more eastern 
faunas, containing two species (see p. 265) that have been found 
far to the north in the Mackenzie River Basin, i.e. Orthis IIcFai- 
lanei and Bhynchonella castanea (N. 67° 15', long. 126° W.). 
Overlying this limestone is the White Pine Shale, a black shale, 
estimated at 2000 feet in thickness, running into red and brown- 
