1902.] DOUGLASS — CKh-TACEOUS AND LOWER TERTIARY. 209 



plored. The basin has no outward drainage, but has several small 

 lakes without outlets, into which small streams empty, when there is 

 an excess of precipitation. The basin is bounded on the south by 

 the high rocky bluffs of the Fox Hills, and on the north, at least in 

 the western portion, by the hard sandstones of the Niobrara and 

 the Dakota (?). The name Lake Basin seems doubly appropriate, 

 for it not only contains lakes, but it resembles the bed of some 

 ancient body of water with bays and inlets, and with capes, pro- 

 monotories and peninsulas extending into it from the southward. 

 The scene is spread out like a great panorama ; the southern hills 

 and northern ridges become hazy in the distance and the farther 

 border seems a dim ridge on the eastern horizon. At the foot of 

 the Fox Hills bluffs are the Fort Pierre shales and still farther away 

 the Fish Creek beds. 



As the principal object of this paper is to show something of the 

 characters of the uppermost Cretaceous and Lower Tertiary forma- 

 tions in this locality, and to give a little light tending toward the 

 clearing up of the problem concerning the boundary between the 

 Mesozoic and the Cenozoic ages in the Rocky Mountains, I will 

 give only a brief sketch of the formations lower than the Niobrara. 



Jurassic, etc. 



The supposed Jurassic is exposed in a dome-shaped uplift, so that 

 the strike of the outcrop is nearly a circle. The beds are sand- 

 stones and sandy clays. The latter are largely red in color. This 

 is apparently due to the combustion of coal. There are bones of 

 large Dinosaufs and of some smaller reptiles, but they have not been 

 studied. It is possible that this stratum with the sandstones above 

 may belong to the Lower Cretaceous. There are many hundreds 

 of feet of hard sandstones and shales between the fossil-bearing 

 horizon and the Fort Benton. The upper portion probably belongs 

 to the Dakota formation. 



The I'ori Benton Formation. 



These beds and their ^contained fossils are much like the cor- 

 responding ones in other regions. They are principally dark shales 

 with bands of sandstone in the lower portion, and in one place I 

 found a half dozen specimens of Frionocyclus Meek in brown con. 

 cretions in the shales. Higher were Ammonites^ Scaphites, Inoce- 



