Ifesozoic and Ccenozoic Geology and Palceoritology. 255 



stone, ofi-anite, syenite, and sometinie& 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 count}-, 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, ver}' 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, chalcedon}^, and manganese of the 

 bottom become more commingled toward the upper inch or half inch, 

 where the silica must have been sufficiently fluid to allow the man- 

 ganese to assume the form of sprig crj^stals. This peculiar deposit is 

 common on all the high hill-tops of Wallace count}^ 



In King's Geo. Sur.,* the Tertiary is divided into Eocene, Miocene, 

 and Pliocene, each of which is again subdivided in. ascending order as 

 follows. Eocene — 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 S3'nonym 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. 



