202 The American Geologist. OctolK-r, i89fi 
<!Overies! in Colorado and the critical reviews of White* and 
Wardf have practically settled the question for all time. 
Time has shown that this conclusion of Dr. Newberry is 
correct, and as the name seems the only fitting and proper 
term by which to designate a formation of wide geographical 
extent in the region of the great plains of the Northwest, oc- 
curring from Dakota westward to the Rocky mountains, it is 
fitting that the name should be defined, its meaning clearly 
given, and the reasons for its use concisely stated. 
The object of the present paper is to show that there is in 
Montana a group of strata, including those originally called 
Fort Union, which overlie and are of latter age than the post- 
Laramie (Livingston) beds; that these beds are of fresh- 
water origin, characterized by a distinct flora of Eocene types; 
and that the series is entitled to recognition as a distinct for- 
mation upon lithological, stratigraphical. and paleontological 
grounds. 
rnlroductort/. — The sedimentary beds exposed in the bluffs 
of the Missouri river at the confluence of the Yellowstone, 
where the former military post of Fort Union was situated, 
were the first lignite-bearing beds of the great plains region 
thoroughly explored by Meek and HajJ^den. Extensive collec- 
tions of the fossil plant remains from these beds were made 
by Dr. Hayden, which were placed in the hands of J*rof. J. S. 
Newberry for study. A large portion, possibly all of the 
plants described by Newberry in his Later Extinct Floras,\ 
came from the valley of the Yellowstone. This valley was 
explored by the part}'^ to w^hich Hayden was attached, for a 
distance of 100 miles or more above the mouth of the river. 
The plants were brought down to Fort Clark and were labeled 
Fort Union. The Eocene age of this fossil flora was recog- 
nized by Newberry, but the failure of Dr. Hayden to discrimi- 
nate the formation from the Laramie caused much discredit 
to fall upon fossil plants as criteria of the age of strata, and 
proved one of the chief hindrances to a true understanding 
of the age and relations of the Laramie group. 
*Synop8is of the Flora of the Laramie group. 6th Ann. Rep. of the 
Director of the U. S. Geological Survey. 
fBuU. 82, U. S. Geological Survey. Cretaceous. 
JN. Y. Lye. ISat. Hist., IX. 1869. p. 27. 
