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Mesozoic aad Cenozoic Geology and Paleontology. 1138 
stone, granite, syenite, and sometimes fragments of fossil wood from an 
older formation. These portions of the deposit, when crumbled, and 
the finer parts washed away, have much the appearance of drift, and 
have been mistaken for it. 
At Breadbowl Mound, Phillips county, it is about 200 feet above 
Deer creek, and at Sugarloaf Mound, in the western part of Rooks 
county, it is about 300 feet above the Solomon river. On Prairie Dog 
creek, in Norton county, it is 400 feet in thickness, and in the extreme 
northwestern part of the State it is still thicker. The formation like 
all the rest in the State, appears to dip slightly to the northwest. 
In the southern portion of the Pliocene, in the vicinity of Fort 
Wallace and Sheridan, the hill-tops are covered with a stratum about 
eight feet in thickness, very hard and siliceous. The material varies 
from coarse flint-quartz to chalcedony. The latter mineral shades 
from milk white to transparent, sometimes presenting a semiopal ap- 
pearance. The so-called moss agate is found in the upper few inches 
of the stratum. ‘This cap rock is interesting to the mineralogist by 
showing the moss agate in its various stages of formation. The lower 
portion of the eight feet indicates an imperfect chemical solution of 
the silica and black oxide of manganese, therefore the crystalization 
of the latter is imperfect. As we examine the strata from the bottom 
to the top, we find the chemical conditions more favorable and com- 
plete, so that the distinct quartz, chalcedony, and manganese of the 
bottom become more commingled toward the upper inch or half inch, 
where the silica must have been sufliciently fluid to allow the man- 
ganese to assume the form of sprig crystals. This peculiar deposit is 
common on all the high hill-tops of Wallace county. 
In King’s Geo. Sur.,* the Tertiary is divided into Eocene, Miocene, 
and Pliocene, each of which is again sub-divided in ascending order as 
follows. Kocene—1. Vermillion Creek Group ; 2. Green River Group; 
3. Bridger Group ; 4. Uinta Group. Miocene-—1. White River Group; 
2. Truckee Group. Pliocene—1. North Park Group; 2. Humboldt 
Group ; 3. Niobrara Group ; 4. Wyoming Conglomerate. The “ Ver- 
million Creek Group,” is a synonym of the Wasatch, and the “ Uinta 
Group,” of the Brown’s Park Group, and worse than all, the ‘‘ Niobrara 
Group” was a pre-occupied name for a Cretaceous Group. 
S. F. Emmons estimated the Eocene of the Green river basin at 
7,500 feet in thickness. The beds of the Wasatch series, which are 
* Geo. Sur., 40th Parallel. 
