122 RECONNAISSANCE FROM CARROLL, MONTANA, 
feldspar. For a distance of two miles, the inclination remains the same; the rock standing up in a 
series of wave-like ridges, all having an abrupt side toward the west, and a gradual slope to the 
east. Looking from the eastern side, the existence of the abrupt rock exposures would hardly be 
expected, so gradual is the rise of the grassy slopes. From the west, on the contrary, the eye is 
immediately struck by the remarkable series of hills with precipitous fronts. 
Some five miles from the road-crossing, there is a sudden change of dip, and as sudden a 
return to the easterly direction: this is very probably a local change, occasioned possibly by a dike 
of igneous rock noticed at that point. The rock is here generally a sandstone, auswering more or 
less closely to the description given above, sometimes a sandy slate, sometiines a whitish-gray sand- 
stone. At the headwaters of Cottonwood Creek, about six miles from the road, we found an 
exposure of a brown sandy slate, full of fucoidal remains, and containing a few indistinct shells. 
As this rock is apparently one of the lowermost layers in the group of rocks being described, these 
fossils are ef interest as furnishing a clue to the thickness of the strata. The fossils are very poorly 
preserved, but have been identified by Mr. Whitfield as follows: 
1. Crassatella, sp. 
2. Crassatella, near cnough to C. vadosa, Morton, to have come from New Jersey. 
3. Inoceramus, sp. 
4. Pholadomya, sp. 
3. Gryphwa, sp. 
6. Panopaa, sp., very near LP. occidentalis, M. & H. 
7. Scaphites larveeformis, M. & II. 
Scaphites larevaformis is regarded as characteristic of Dr. Haydeu’s No. 2. Above this bed 
there mast be 5,000 fect of rock belonging to the Cretaceous, though referred in part by Dr. Hayden 
to the Coal Group. 
At the point mentioned we pass a deep grassy valley a few hundred feet in width, and on the 
other side rises along range of high bluffs 100 feet above, aud extending for a mile or more (see fig. 12), 
, The rocks are exposed for a height of from 10 to 
Vig. 12. dete : 
50 feet in the perpendicular eastern front of the 
bluffs, and form a feature of the country quite 
conspicuous even from a distance. The rock is 
2 a brown and gray sandstone in alternate layers, 
a eae ae with occasional slaty bands. The dip is here 
westerly, it being the under part of a very long 
aud low fold. From the summit, quite a good view is obtained to the west; the bluff hasan abrupt 
front both to the east and northwest. The valley alluded to occupies the position of the axis of 
the anticlinal, and the fold itself is a continuation north of the folding which took place in the 
Bridger Range. 
Turning north from here, we crossed the divide a mile beyond, and came into a long valley 
which trends a little west of north. The rock observed here was a brownish-yellow sandstone, with 
a clay-shale underlying it, aud is undoubtedly Cretaceous, though containing no fossils. The valley 
alluded to drains into Sixteen-mile Creek. We followed it for a distance of ten miles, keeping 
along with the strike of the rocks, and found it abundantly covered with thick grass, or rather at 
this season with hay cured in the ground, which could afford grazing for multitudes of cattle. 
Turning again easterly, across the strike of the rocks, we cross a long series of wave-ridges dipping 
_east as before, and much resembling those previously observed. A very white fine-grained sandstone 
forms a series of bluffs not much west of the road. 
The valley of the south branch of Deep Creek is wide and level. Ou the northeastern side, 
where the road to the Forks of the Musselshell turns off to ascend the divide, there is quite a high 
ridge, extending from the end of the Elk Range across toward the Crazy Womaw’s Mountains. 
This valley is obviously, like its continuation below, a synclinal, for the strata dip sharply to the 
west 70°, the strike being the same northwest. The same dark-colored sandstone forms the first 
layer: this is underlaid by a sandy slate with large clay cannon-ball concretions. From here on for 
a mile, the dip is continuously westerly, there being the same series of wave-ridges observed before, 
