TO YELLOWSTONE NATIONAL PARK. 133 
At Camp Baker, Primordial fossils were found in a limestone hill to the northwest of the Post; 
the series and the estimated thickness are as follows: Quartzite, 20 feet; variegated shales, 
mostly bright-red, also green and blue, 150 fect; limestone, in a double series of ledges, 80 feet ; 
quartzite, reddish, slightly micaccous, then @ series of colored slates, mostly green, followed by 
shales and thin beds of sandstones and limestones, in all probably 1,500 feet ; still further con- 
formable shales, 1,000 feet. These extend toward the north farther than we could follow them It is 
enough to say that the total thickness of the conformable strata underlying the fossil-bearing 
limestone cannot be less than 3,000 fect, and is probably much more. All the facts point to a 
very great development of Lower Silurian rocks. 
The saine rocks were ideutitied at Moss Agate Springs at the south extremity of the Elk Range 
of Mountains; we found here red shales like those at Camp Baker, quartzite and limestone, the 
latter containing many fragments of Trilobites. We were able only to glance at this locality, aud 
consequently the observations stand out isolated. To the Primordial we refer also the rocks 
underlying (in position overlying, in consequence of au overturn) the Carboniferous limestone of 
the Musselshell Cation, of which there must be a thickness exposed of some 1,000 feet. It is also 
very probable that the limestone and red shales of the east bank of Deep Creek observed in iso- 
lated patches belong to the same time. With the exception of the above, no rocks older than the 
Carboniferous were seen by us anywhere from Carroll to Fort Ellis. It is certainly not to be 
affirmed positively that they do not exist in the mountains touched at; the contrary is probable, 
but it is quite certain that, if present, they are in all cases subordinate. 
Carboniferous.—Carboniferous rocks are largely and very uniformly developed over this part of 
the Northwest, as has been remarked by Dr. Hayden. All of the minor ranges of hills, repeatedly 
referred to, contain Carboniferous limestone to a large extent. In fact, the most striking and char- 
acteristic features of all these minor ranges are the walls of white limestone, which stand up con- 
spicuously above the timber, and attract the attention even from a great distance. The very 
uniform nature of this limestone has been noted, and to its character in weathering out into steep 
walls and isolated towers is due the conspicuous appearance mentioned. The general facts in regard 
to this formation, collating those obtained at different places, may be summed up as follows: The 
upper portion consists of limestone in thin beds, with layers of shale and a little sandy slate. These 
upper layers contain fossils more abundantly than the following beds. Produetus, Chonetes, Spirifera, 
Athyris, Rhynchonella, and Streptorhynchus ave abundant forms. At the Bridger Mountains, some 
bands of red clay in the upper part of the formation were very conspicuous and persistent, and sug- 
gestions of them were seen elsewhere. At Cinnabar Mountain, in the Yellowstone Valley, the 
intensely red clays and shale, from which the mountain derives its name, immediately overlie Car- 
boniferous limestone, and belong, as elsewhere, to the upper part of the formation. Below these 
irregular, thin beds, showing a somewhat different character at different localities, comes the mass 
of the limestone already many times described. It is firm, bluish white, and always cherty. The 
flint is sometimes in uniformly-distributed particles of small size, sometimes in broad bands. When 
acted upon by the weather, the rock takes the form of vertical walls and steep towers, show- 
ing no trace of stratification. Reference must also be made to the remarks of Mr. Whitfield upon 
the fossils found by us at the Little Rocky Mountains. Hesays: “The general expression of these 
fossils is that of Low Carboniferous, or perhaps Waverley.” To this, we can add nothing, except 
that the fossils came from a limestone underlying the massive blue limestone before spoken of, con- 
taining Zaphrentis and other corals in considerable abundance. Hxcept at this point, we found 
nothing to suggest the possible occurrence of any rocks between the Primordial and the usual 
Carboniferous. 
As to the total thickness of the Carboniferous formation as here developed, we can only hazard 
a conjecture, which cannot be of very great value. The compact limestone spoken of must be at 
jeast 500 feet in thickness, and the total may be 600 feet. At any rate, it is certain that the 
deposits point to a uniform condition of things at the time when the formation was laid down. 
Jurassic.—J urassic fossils were found on the east slope of the Bridger Mountains at both points 
where the ascent was made. The only rock observed was limestone, and the fossils were quite 
abundant, in some layers, at least. The thickness seen was small, and on the one side was a 
Cretaceous fossil-bearing sandstone, and on the other the undoubted Carboniferous limestone. The 
