242 F. V. Hayden on the Geology of the Country 
fifteen miles east of the mouth of that creek. Often the beds 
seem to have been raised up several hundred feet above their 
original position, without inclination, resting upon the upturned 
edges of the lignite beds which we have before observed, par- 
took equally of the disturbing influences which have given so 
great an inclination to the older fossiliferous rocks. Along the 
Big Horn mountains and the North Platte the lignite beds some- 
times incline from the foot of the mountains 80° and often the 
influence of the elevatory power has affected them far out into 
the plain country. 
In the above accounts of the Tertiary deposits of the West we 
have shown that the older members are clearly separated into 
four divisions exclusive of the Pliocene deposits of the Niobrara. 
Let us examine the evidence in regard to the age of these de- 
a If we study the upper portions of Cretaceous formation 
o.5 when not removed the erosive power of water to 
any great extent, we then observe from the time we pass from 
No. 4 to No. 5 a gradual change in the sediments and other in- 
dications of a slow approach to shallow water, arenaceous sedi- 
ments begin to take the place of argillaceous so that we have 
alternate thin layers of sand and clay, the sand continuing to 
We have also mentioned the fact that the fossils of upper pat 
No. 5 seem to have existed upon the verge of the Tertiary period, 
that they eo present peculiar forms more closely allied to 
of the genera Buculites, Ammonites, Inoceramus, ete., which are 
every where supposed to have become extinct at the close of the 
Cretaceous epoch, we would be in doubt whether to pronounce 
em Tertiary or Cretaceous. These facts would seem to ind 
cate a foreshadowing of the Tertiary era and that the transiioB 
from one great period to the other was gradual and quiet, ie 
change in the physical conditions being ultimately sufficient 
