424 Scientific Intelligence. 
saw this formation at two or three points above Fort Union. In ama 
accompanying a highly interesting memoir on the geology of the Hud- 
son’s Bay Territories, published recently by Mr. A. K. Isbister, in the 
Journal of the Geological Society of London, a large area about the 
sources of the Missouri, is colored as Tertiary, but so as to convey an I- 
correct idea of the extent of country occupied by it. About the same 
stone, surmounted along the west shore of that stream by Cretaceous 
outliers. Between this and the Black Hills he brings up to Cannon-ball 
River, from the White River basin, a continuous belt of Tertiary. West 
of this he places a belt of Jurassic, and along the supposed position of 
In all this Mr. Marcou is certainly mistaken, excepting in regard to the 
i i a 
far north by two or three hundred miles, as laid down by him. 
Leaving for a future occasion all local and other details, we now pro- 
pose to give a brief general sketch of the extent and boundaries, as far 
as we can, of that portion of the great Tertiary lignite formation from 
which our fossils were collected, with a few remarks upon its probable 
age, and relations to the White River basin, as well as to the Cretaceous 
formations upon which it reposes. : 
Ascending the Missouri from Fort Pierre, we find on reaching @ point 
five miles below Heart River, about the 47th parallel north, that the Cre- 
taceous formations which are so conspicuous for many hundred mi 
