TO YELLOWSTONE NATIONAL PARK. 113 
MUSSELSHELL CANON TO CAMP BAKER. 
The Musselshell Cajion divides the Little Belt Mountains from what is called the Elk Range. 
It is a narrow mountain-ravine, with steep hills on both sides, which sometimes approach very 
closely together, and again recede, giving room for a little strip of green meadow-land on the border 
of the stream. It is, throughout its length of eight miles, very picturesque, especially near the 
eastern end, where the abrupt walls and buttresses of white limestone contrast strongly with the 
dark-green foliage of the pines and spruces. All together, it was a most delightful relief from the 
parched alkaline prairie on which we had made our camps for the preceding fortnight. The waters 
of the stream are clear and cold, and abound in what is apparently a species of Coregonus. This 
fish rose readily to a fly, affording to some members of the party fair sport, and furnishing a very 
agreeable variety to the sameness of our daily fare. 
On leaving the open country and entering the cafion, we came abruptly upon the Carboniferous 
rocks. A band of red clay a few feet wide is quite conspicuous at its eastern opening, followed 
by several others less striking and quite narrow, all red or ocher-yellow. These are interstratified 
with a sandstone which contains great numbers of Ostrea congesta, Con., as identified by Mr. Whit- 
field. These dip west 50°. Immediately following these are successive layers of limestones and 
slates, and then several hundred feet of limestone. 
From the former beds the following fossils were obtained: 
1. Bryozoan (undescribed). 
. Aulopora, or bases of Syringopora. 
. Zaphrentis centralis, Ev. & Shum. 
Productus semireticulatus, Mart. 
Productus muricatus, N. & P. 
Productus, sp., probably young of P. punctatus. 
. Productus, sp., approaches forms referred to P. Prattenanus. 
. Productus multistriatus, Meek. 
. Athyris, sp. 
10. Pinna Ludlovi, Whitfield (n. sp.). 
The overlying limestone-beds all dip like the others, a little south of west, 50° to 60°. These 
limestones form a number of high vertical walls and isolated towers, which are worn out into a 
variety of fantastic forms which have already been alluded to. These are especially conspicuous 
on the north side of the stream, though similar walls are seen too on the other side in the line of 
the strike. This limestone is very cherty, the fragments of flint being numerous; and it is to their 
presence that the rock owes the peculiar forms in which it now appears. The walls show no evi- 
dence of structure or stratification. They abound in little cavities and holes, often partially 
filled with stalactitic masses of carbonate of lime, showing the extent to which the solvent action 
of water has worked upon them. 
A similar relation of the rocks was observed on the upper slopes of the Bridger Mountains ; 
that is, the series of bright-red indurated clays, with a little Cretaceous sandstone, followed by thin 
layers of limestone full of Carboniferous fossils, and then 500 feet or more of a firm cherty limestone, 
weathering out into walls showing no stratification and rarely containing fossils. The limestones are 
overlaid by (Jurassic and) Cretaceous and underlaid by Silurian. The similarity in the succession 
of the beds makes it quite certain that the underlying rocks at the entrance of the Musselshell 
Cafion are really the youngest, forming the upper part of the Carboniferous series, while the rocks 
which follow and overlie, apparently conformably, are older, and, in part at least, Lower Silurian. 
The later layers of the limestone, going west through the caiion, have a somewhat different 
look from those seen farther to the east, being darker-colored and more uniform in appearance. 
Leaving the limestone, we passed over perhaps a quarter of a mile without finding any rock in 
place, though on the hill-slopes to the south masses of a hard, reddish quartzite indicate the pres- 
ence of this as a member of the series. The next exposure reached was an argillitic slate, with 
veins of quartz, also dipping westerly. The hills for a considerable distance are rounded and 
covered with grass, exposing no rocks within the limits that we were able to cover. 
The prevailing rock, as we continue up the caiion, following the course of this branch of the 
15 w 
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