TO YELLOWSTONE NATIONAL PARK. 107% 
mine the age of the rock to be Carboniferous. The following is a list of the fossils obtained at this 
oint : 
: Crinoidal remains too indistinct to be identified. 
Terebratula or Cryptonella. 
Spirifera (Martinia) lineata, Martin. 
Spirifera centronata, Winch. 
Orthoceras? ??, possibly filling of outer chamber. 
Spirifera centronata, Winch., was the most abundant and characteristic form noticed here. 
The thickness of these limestone beds must be very considerable; at least 300 or 400 feet were 
seen on this side of the hill, but as we were unable to foliow them farther, we cannot venture to 
estimate their whole extent. This limestone is intersected at one point by a ridge of hard trachyte. 
On the other side of the little creek valley, the limestone also appears, containing here only a 
few imperfect crinoidal stems. Here it is apparently overlaid by a sandstone which has all the 
appearance of dipping under the hill, or, in other words, is overlaid by the trachyte. The outlying 
hill, f, is made up of sandstone, or a sandy slate; its summit is 1,200 feet above Box Elder, and hence 
a thousand feet lower than the adjoining trachytic hill. The observed thickness of this slate is 200 
feet; dip 10° a little east of north, and strike nearly east and west. It can hardly be conformable 
to the limestone described; but the eruption of the trachyte, which doubtless accompanied the 
elevation of the mountains, has very much complicated the relations of the beds.. 
This slate contained large numbers of poorly-preserved fish-scales, which would seem to show 
its probable identity with the elevated slates in the ravine behind Cone Butte. Further than this, 
its position seems to suggest that it may be nearly parallel with the sandstones near Cone Butte, 
which are, as has been stated, Upper Cretaceous. No trace was seen at this point of any rocks 
between the Cretaceous and the Carboniferous limestone. 
gu bop 
FROM BOX ELDER TO CAMP LEWIS. 
The road from Box Eldez to Camp Lewis follows along the foot of the mountains, but at such 
a distance from them that very few observations could be made. The character of the country is 
much better than that nearer the Missouri, but cannot be very highly praised. The Judith Mount- 
ains give rise to several running streams, which occupy wide valleys, and the region seems well 
adapted for stock-raising. Near Armell’s Creek, a mile to the north of the road-crossing, gray clays 
are conspicuous, forming high bluffs with perpendicular faces, quite different from anything seen 
near Crooked Creek. This exposure was visited later, on the way to the mouth of the Judith 
River, but yielded no fossils, and its age is therefore uncertain. It is probably, however, near the 
top of the Cretaceous. 
Our road approached quite near the mountains at Bald Butte (see m on map), and here,and at 
several points beyond, we observed a considerable thickness of a soft white sandstone, fine-grained 
and even-textured, but without fossils. It is in very thick beds, and weathers out in vertical walls, 
taking fantastic shapes, which are like those of the “Quader Sandstein” of the Saxon Switzer- 
land. This is undoubtedly Upper Cretaceous. From this point, the road bears away from the hills 
again, crossing the divide between the Musselshell and Judith Rivers, and passing between the 
Judith and Moccasin Mountains. As has been before remarked, the dark clays of the Fort Pierre 
Group are seen again south of the Moccasin Mountains and just before reaching Warm Spring 
Creek. At this point, there was a considerable exposure of these beds, and, although no fossils 
were collected here, the characteristic features of the deposit were unmistakable. Farther on, a 
cut bank on the creek gave the following section : 
Yellow clays, somewhat sandy ....-.----..-----+-e+eeeee di Bee Sawing es ails 20 feet. 
Hard gray shaly clays Seen. ..----.--- 6-2 ene eee ene ce eee eet e tere eee eeee 20 feet. 
These beds had a very slight dip a little cast of north. 
The Moccasin Mountains we were unable to visit; but their appearance, as viewed from vari- 
ous points on the road, and again from the northeast, indicated that, like the Judith Mountains, 
they are largely trachytic. 
Camp Lewis is situated on Trout Creek, or Big Spring Branch, as it is sometimes called, which 
