XXXIV INTRODUCTORY REMARKS. 



This division occupies a considerable area of country around Fort Pierre 

 and between there and the Bad Lands, as well as at intervals between the 

 Bad Lands and the Blaek Kills. In the region of Fort Pierre, it forms the 

 entire hills bounding the immediate valley of the Missouri ; and above the fort 

 it extends northward to the region of Cheyenne and Moreau Rivers, where it 

 dips beneath the Fox Hills group, though it continues to be seen in the bluffs 

 along the Missouri and other streams for some distance above. It likewise 

 appears again, and forms much of the surface of the country on the distant 

 Upper Missouri country on Milk and Muscleshell Rivers in Montana. It 

 also extends far northward into the British possessions, some of its character- 

 istic fossils having been identified by the writer among collections brought 

 by Professor Hind and Professor Dawson, in charge of Canadian government 

 exploring parties, from the Saskatchewan and Assiniboine countries, in 1858 * 



On the Yellowstone River, at a locality one hundred and fifty miles above 

 its mouth, in Montana, outcrops occur presenting the lithological characters 

 of this formation, and containing great numbers of its characteristic fossils, 

 directly mingled with many of those elsewhere only found in the Fox Hills 

 beds above. 



This rock also forms the hills on both sides of the Missouri below Fort 

 Pierre to the Great Bend, just below which, as elsewhere stated, its base is 

 seen resting on the upper uneven surface of the Niobrara group. From the 

 Great Bend down to the mouth of the Niobrara River, in Dakota and 

 Nebraska, the country on both sides of the Missouri is made up of these two 

 formations; and the Fort Pierre group finally runs out in the form of outliers 

 on the tops of the hills below the mouth of the Niobrara. So far as known 

 to the writer, this formation has not been certainly identified along the irreg- 

 ular outline of the outcrops of the older members of the series seen extending 

 southward and southwestward, through Eastern Kansas and Nebraska, 

 much beyond the points where it. runs out on the tops of the hills, as men- 

 tioned above, near the mouth of Niobrara River. A tew of its characteristic 

 fossils, however, have been found in Texas and New Mexico; and Messrs. 

 Holmes, Marvine, Peale, and other members of Dr. Hayden's party, have 

 also brought a lew of the same forms from Western Colorado. 



From the statements of the gentlemen who have visited these districts, 



'See Report uf Explorations between Lake Superior and the Red River Settlement (Toronto, 

 18, 1859); and Professor Hind's Report of the Saskatchewan and Assiniboiue Expedition, 182J 1859. 



