INTR0D1 rCTORY REMARKS. X X I X 



resting on granite, as far eastward as Sauk Valley, Minnesota, from which 

 locality a few of its characteristic fossils were, some years back, sent to the 

 writer by Mr. I. H. Kloos* Here it presents its usual lithological characters, 

 and also contains a few thin seams of impure lignite. 



From the localities mentioned, along the Missouri near and above the 

 mouth of Big Sioux River, outcrops of this rock range in a south and south- 

 westerly direction through Eastern Nebraska and Kansas into the Indian 

 Territory; and it apparently also occurs in Arkansas. For the reasons 

 already mentioned, however, it is not generally well exposed, only a slope 

 being, in most cases, observed at its horizon. Dr. Newberry and others have 

 brought some of its characteristic fossils from New Mexico, and Mr. Holmes 

 from Southwestern Colorado, where it is said to contain some valuable beds 

 of lignite. Dr. Shumard also identified it in Texas. At these southern 

 localities, as well as in Wyoming, this formation is more arenaceous than 

 farther northward and eastward. 



Dr. Harden has likewise brought fossils from this rock at various local- 

 ities along the eastern base of the Rocky Mountains, northward to the Black 

 Hills, and again from far uj;> the Missouri near Fort Benton, where it is exten- 

 sively developed and more than usually fossiliferous, from which facts it has 

 been named the Fort Benton group. In this region, it is supposed to attain 

 a maximum thickness of from six to eight hundred feet. 



The highest northern point from which we have had any indications of 

 the existence of this rock is on the north branch of the Saskatchewan, about 

 thirty miles west of Fort A la Corne, near the 54° of north latitude, where 

 Professor Hind discovered fossils that were referred by the writer to this 

 horizon.f Prof. S. J. Dawson also discovered others at a locality two hundred 

 and fifty miles west of Fort Garry, on the Assiniboine, British America, that 

 were likewise referred in the same way to this formation. J 



Some of the fossils of this rock were likewise brought by Dr. Hay den's 

 party from Cinnabar Mountain, Yellowstone Valley, Montana. (See Hay- 

 den's Sixth Report U. S. Geol. Survey of the Territories, page 475, 1873.) 



On the Union Pacific Railroad in Wyoming Territory, five miles east of 



* See Am. Jour. Sci. and Ails, IsT'J, p. 17. 



t See Professor Hind's Report on the Saskatchewan and Assiniboine Exploring Expedition, 179. 

 Toronto, 1859. 



{Professor Dawson's Report on Explorations of the Country between Lake Superior and the Red 

 River Settlements, 13. Toronto, 1859. 



