, Geology. 425 
west branches of the Cheyenne. Cannon-ball river, Watahoo, and other 
small tributaries, however, cut down to the Cretaceous beds some little dis- 
tance back from the Missouri. On the east side of the Missouri the Ter- 
iary is bounded on the south, nearly opposite the mouth of Cannon-ball 
r 
near the Missouri to about 102° of west longitude, where it: is inter- 
rupted by a small tributary of the Cheyenne. West of this small stream, 
the same range of Upper Cretaceous hills, known perhaps by other local 
names, bears round to the northwest, crossing the head branches of the 
Little Missouri so as to strike the Yellow-Stone river about ten miles,be- 
low the mouth of Powder river; forming nearly all this distance the south 
in this way, it must be borne ii mind that the Black Hills are laid down 
on most of the published maps of this country as extending a long dis- 
tance too far north. 
Returning to the point near Heart river, from which we first set out, 
we find on ascending the Missouri, that the Cretaceous strata again rise 
localities the Prince of New Wied collected a nearly entire skeleton of 
Sequence of their inclination to the east or northeast. On the nort 
side of the Missouri, between it and Milk river, the higher portions of the 
country back from the Missouri, are also composed of Tertiary beds 
Th : 
shell river, where they thin out on the summits of Cretaceous hills. The 
ills, however, near the Missouri, between Milk and Muscleshell rivers, 
also mainly Cretaceous, the Tertiary being for the most part worn 
away by atmospheric agencies. 
0 i Yellow-Stone, only Tertiary strata are seen from 
Oe ees Powder i far it the mouth of the Big Horn. 
ceived Tertiary fossils from intelligent traders, collected as far up the Big 
Horn as one of its tributaries known as Little H 
Some as far west on the Yellow-Stone as Rose river, we received a few 
retaceous fossils. As to the limits of the Tertiary up Powder and 
SECOND SERIES, VOL. XXII, NO. 66.—NOV., 1856 
54 
