2 24 KNOWLTON 



present they are regarded as being slightly older than the beds under 

 discussion, though of Eocene age. 



It is not deemed necessary in the present connection to attempt 

 a further analysis of the relations between this flora and that of other 

 Eocene and the Miocene. The number of common species show 

 the direction in which the affinities lie. 



b Paleohotanical Proof of the Eocene Age of the Fort Union Flora. 



As stated in the opening pages of this paper little doubt is now 

 entertained as to the Eocene age of the Fort Union. So long, how- 

 ever, as it was confused with the Laramie and other formations, 

 attempts at interpreting its floral affinities could but lead to conflict- 

 ing or indecisive results. Thus, in 1886 Professor Ward^® insti- 

 tuted an elaborate investigation to ascertain the Cretaceous or Ter- 

 tiary age of the 'Laramie,' which was destined to failure, as it in- 

 cluded plants from beds now known to belong to the Montana, Lar- 

 amie, Arapahoe, Denver, Livingston and Fort Union. It should 

 not be supposed, however, that he failed to note the well-marked dif- 

 ferences between the flora of the Fort Union and that of the other for- 

 mations considered with it. He saw these clearly enough, and pointed 

 them out, but was misled by the prevailing opinion of the time, 

 mainly that of the invertebrate paleontologists, that it could not be 

 separated from the 'Laramie,' just as Newberry had been earlier 

 misled into referring the Fort Union to the Miocene, on the basis 

 of the then current correlation of certain plant-bearing horizons 

 in Greenland, England and elsewhere. But as early as 1875, Sir 

 William Dawson and Dr. Geo. M. Dawson^^ maintained the Eocene 

 age of the Fort Union (the "Upper Laramie" of Canadian geolo- 

 gists), and neither one, so far as known to the writer, ever changed 

 this opinion as to its position. 



The flora of the Fort Union, as Newberry stated, has a botanical 

 facies that permits at a glance its separation from that of the Lara- 

 mie. It clearly inaugurates a new order of events and witnessed 



•"' Synopsis of the Flora of the Laramie Group; Sixth Ann. Rept. U. S. 

 Geol. Surv., 1884, 1885 (1886), pp. 399-557, pis. 31-65. 



"Brit. N. A. Bound. Com., Geol. & Resources Vic. 49th Parallel, 1875, 

 pp. 183-202. 



