18 



bluffs west of the fort, which were composed of the blue bed, capped by a 

 thinner layer of the yellow. Large globular or compound globular argillace- 

 ous concretions coated with gypsum were abundant at this point. 



"Along the Smoky Hill River, thirty miles east of Fort Wallace, the south 

 bank descends gradually, while the north bank is bluffy. This, with other 

 indications, points to a gentle dip of the strata to the northwest. The yellow 

 bed is thin or wanting on the north bank of the Smoky, and is not observable 

 on the north fork of that river for twenty miles northward, or to beyond 

 Sheridan station on the Kansas Pacific Railroad. Two isolated hills, 'The 

 Twin Buttes,' at the latter point, are composed of the blue beds, here very 

 shaly, to their summits. This is the general character of the rock along and 

 north of the railroad between this point and Fort Wallace. 



" South of the river, the yellow strata are more distinctly developed. Butte 

 Creek Valley, fifteen to eighteen miles to the south, is margined by bluffs of 

 from twenty to one hundred and fifty feet in height on its southern side, while 

 the northern rises gradually into the prairie. These bluffs are of yellow chalk, 

 except from ten to forty feet of blue rock at the base, although many of the 

 canons are excavated in the yellow rock exclusively. The bluffs of the upper 

 portion of Butte Creek, Fox and Fossil Spring (five miles south) Canons are 

 of yellow chalk ; and the reports of several persons stated that those of Beaver 

 Creek, eight miles south of Fossil Spring, are exclusively of this material. 

 Those near the mouth of Beaver Creek, on the Smoky, are of considerable 

 height, and appear, at a distance, to be of the same yellow chalk. 



"I found these two strata to be about equally fossiliferous, and am unable 

 to establish any paleontological difference between them. They pass into 

 each other by gradations in some places, and occasionally present slight 

 laminar alternations at their line of junction. I have specimens of Empo 

 semianceps, Cope, from both the blue and yellow beds ; and vertebrae of the 

 Platecarpus glandiferus, Cope, were found in both. The large fossil of Liodon 

 dyspelor, Cope, was found at the junction of the beds, and the caudal portion 

 was excavated from the blue stratum exclusively. Portions of it were brought 

 east in blocks of this material, and these have become yellow and yellowish 

 on many of the exposed surfaces. The matrix adherent to all the bones has 

 become yellow. A second incomplete specimen, undistinguishable from tliis 

 specie.^;, was taken from the yellow bed. 



"As to mineral contents, the yellow stratum is remarkably uniform in its 



