

AGE OF THE LIGNITE FORMATION, 


and western representatives to different formations. It becomes necessary, 
nif consistency shall be preserved to include the whole series in the Cre- 
taceous or Tertiary, and the former course is adopted. Prof. Meek 
writes :—‘ The occurrence of this last named species here, along with 
a Cretaceous type of reptilian, and a Corbicula apparently identical with 
C. cytheriformis of the Judith River brackish-water beds, together with 
the presence of Corbulas, very closely allied to Judith River species, at 
lower horizons in this series, and the occurrence of some vertebrates of 
Cretaceous affinities at the Judith River localities,would certainly strongly 
2 favour the conclusion, not only that this Judith River formation, the age a 
of which has long been in doubt, is also Cretaceous; but that even the 
higher fresh-water lignite formation at Fort Clarke and other Upper 
Missouri localities may also be Upper Cretaceous, instead of Lower Ter- 
s, 
4T3 
. a 
= 
P) 
-~, 
4 
3 
bes 
tiary.””* 
: 442. Professors Newberry and Lesquereux have investigated the 
. numerous and rich collections of plants obtained from beds associated is 
with the lignites. Prof. Newberry, in 1869, in describing plants ob- ‘3 
tained by Dr. Hayden, throughout refers to the deposits as of Miocene 
age. The specimens examined at this time were from various localities 
in the valley of the Missouri, from the extreme eastern edge of the forma- 
tion at Fort Clark, to a point 100 miles up the Yellowstone.+ Prof. a 
Newberry still maintains the Miocene age of the Upper Missouri lignite an 
beds, on account of the great similarity of their flora to that of the ‘ 
Miocene of other regions, but inclines to refer those of Colorado, Wyom- F 
ing, and Utah to the Upper Cretaceous.{ This arrangement is appar- 
ently quite at variance with the stratigraphical unity of the formation, 
insisted on by Hayden and others, and the resemblance of many of the 
molluscan types throughout. 
443. Prof. Lesquereux, while admitting the Miocene facies of the 
| plants from the lignite deposits, when compared with those of the old 
q world,§ places those of the Missouri basin in the Lower Eocene, and ie 
h includes in the same category the greater part of those of the western 
| Rocky Mountain region. He, however, points out the close correspon- 
i? dence of American Tertiary and Cretaceous forms—plants from the ; 
e lower beds of the Cretaceous haying originally been referred to the 
; Miocene of Europe. Prof. Lesquereux visited and carefully examined 
4 7 some of the most interesting localities in 1872, and appears to have been 

a * U.S. Geol. Surv. Territ. 1872. p. 4 + Geological Report Yellowstone and Missouri Expedition. 
t} Am. Journ. Sci. and Arts, “April. 1874. § Am. Journ. Sci. and Arts, April. 1874. t 

