CRETACEOUS AND TERTIARY FORMATIONS 



545 



It was probably this same White Butte area which was dis- 

 covered by Professor E. D. Cope in September, 1883. The dis- 

 covery was announced in a letter written from Sully Springs, 

 Dakota, and read before the American Philosophical Society. 

 The following is a portion of this letter: 



I have the pleasure to announce to you that I have within the last week 

 discovered the locality of a new lake of the White River epoch, at a point 

 in this Territory nearly 200 miles northwest of the nearest boundary of the 



Fig. 13. — The coarse sandstone of the lower member of the White River beds in 

 White Butte, Billings County, North Dakota, showing effects of rain erosion. 



deposit of this age hitherto known. The beds, which are unmistakably of the 

 White River formation, consist of greenish sandstone and sand beds of a 

 combined thickness of about 100 feet. These rest upon white calcareous 

 clay, rocks, and marls of a total thickness of 100 feet. These probably also 

 belong to the White River epoch, but contain no fossils. Below this deposit 

 is a third bed of drab clay, which swells and cracks on exposure to weather, 

 which rests on a thick bed of white and gray sand, more or less mixed with 

 gravel. This bed, with the overlying clay, probably belongs to the Laramie 

 period, as the beds lower in the series certainly do. 



Then follows a list of 20 species of vertebrates which were 

 collected from this locality, including Trionyx, Galecynus gregarius, 



