TO YELLOWSTONE NATIONAL PARK. 101 
and subdivide again to a wonderful extent, thus carrying the surface-drainage back into the river. 
These ravines are often quite well wooded, and some of them coutaiu a little strongly alkaline 
water. 
As has been remarked, the height of the plateau varies but little as we proceed away from the 
river, though we soon pass over the divide which separates the immediate drainage of the Missouri 
from that of Crooked Creek, a tributary of the Musselshell River. 
Little Crooked Creek, thirteen miles from Carroll, retains water in holes until midsummer, 
wheu it generally dries up entirely. Five miles beyond, a branch of Crooked Creek also affords a 
little poor water in the early summer ; but, late in the scason, the only water on the route is found in 
pools in the bed of Crooked Creek, and this is decidedly unpalatable. AJl these creeks, with their 
many dry branches, certainly contain swiftly-running water in the early season, when the spring 
rains unite with the melting snows to swell the streams, This is plainly shown by the high, cut 
banks and the large accumulations of drift pebbles in the turns in the creek-beds. 
The surface of the prairie from Carroll to Crooked Creek (twenty-one wiles) and beyond, 
though this point is only about fifteen miles from the river in a direct line, is scattered ,with drift 
deposits. These are of two kinds: (1) large, mostly angular, blocks of syenite and other horn- 
blendic rocks, with occasionally some semi-crystalline limestone ; and (2) small, smoothly-rounded 
pebbles, consisting to 90 per cent. of a brown quartzite or jasper. Some fragments of fossil wood 
may here and there be found, and a large variety of pebbles of various kinds of rocks in small 
quantities. This drift is entirely superficial, uo proper deposits having been observed at any point. 
The lithological character of the drift will be described more in detail hereafter, when it will be 
conuected with observations made north of the Missouri River (p. 135). 
At Carroll, in the lower levels of the Cretaceous No. 4, the only fossils observed were Baculites 
ovatus, Say, aud a large Inoceramus. At Little Crooked Creek, where we made our first camp 
(July 13), we had more opportunity for search, and here, and farther on, at Crooked Creek, we found : 
1. Lucina ventricosa, M. & UH. 
. Lucina occidentalis, Morton. 
Mactra, sp.?. 
. Inoceramus tenuilineatus, H. & M. 
. Anchura, sp. (specific. features not shown). 
. Ammonites Halli, M. & H. 
7. Scaphites nodosus, Owen. 
8. Baculites ovatus, Say. 
Lo 
oe ed 
Inoceramus tenuilineatus, H. & M., Ammonites Halli, M. & H., and Baculites ovatus, Say, were 
extremely abundant at these localities, and the specimens secured comprise individuals of all ages. 
These fossils, as far as our observations go, are found only in the concretions previously men- 
tioned in connection with these beds. These concretions occur in great numbers from the level of 
the river to the highest point above it where these clays were seen. Those which contain fossils 
seem to be much more abundant in the upper layers than in those nearer the water’s level. Fossils 
were occasionally found in concretions from the lower ravines ; but such concretions were not seen 
in place, They were generally found imbedded in the loose, washed clays of the ravine, and had 
the appearance of having been carried down from some point above. The concretions are quite 
compact when found in place in the cut bank, though they yield readily to a blow of the hammer. 
Whenever exposed for any length of time, however, to atmospheric influences, they separate into 
hundreds of angular fragments ; and here and there over the prairie may be seen the little piles of 
these blocks, a conspicuous feature among the low cactus-plants. 
The concretions are generally a foot or two in diameter, though sometimes much larger, and 
are extensively cracked ; the seams having been filled with crystallized calcite and sometimes with 
gypsum. One fine specimen of an Ammonite was found, the interior of which was lined with exceed- 
ingly delicate crystals of the selenite. The concretions, as a rule, are not distributed at raudom 
through the clays, but lie in layers, sometimes closely contiguous, so as to form an almost uninter- 
rupted stratum. The large majority are destitute of fossil remains; but occasionally they are met 
with, containing large numbers of the shells, a considerable number forming the nucleus of a single 
