14 GEOLOGY OF THE TERTIARY FORMATIONS OF 



Cn the map I have designated both deposits, whic'i are remarkable for containing 

 the ren ains of vertebrata in great numbers, by one color, and in describing I have 

 regarded them as forming one great basin. The Miocene fauna of the White River 

 beds is entirely distinct from that of the Pliocene beds of the Niobrara and Loup 

 Fork, and it is quite possible that a more careful study of the relations of these two 

 deposits to each other may result in separating them completely. The sediments 

 which compose the Pliocene beds appear to have been derived almost entirely from 

 the eroded materials of the White River group, and the two groups evidently sustain 

 some relation to each other in time, while the two seem to have no connection, either 

 lithologically or pal^eontologically, with any other Tertiary deposits on the Upper 

 Missouri, unless with the Wind River deposits, which are comparatively slight. The 

 erosion of the Pliocene beds does not give to the surface of the country that wonder- 

 fully unique character which is so well shown on White River, but it undoubtedly 

 supplies the materials for a singular formation called the Sand Hills, which are a 

 striking feature of the country. That portion of Nebraska usually called the " Sand 

 Hills " occupies an area of at least 20,000 square miles, and gives to the surface of 

 the country, as far as the eye can reach, the appearance of a continued series of 

 conical hills of sand, constantly wrought upon by the wind, so that it is even 

 now slowly moving from point to point. Many of these hills have much the 

 appearance of craters, the wind, as it were, scooping out a circular hole in the top. 

 This is perhaps the most sterile portion of the West, and yet it is by no means 

 destitute of vegetation. A variety of plants, including some grass, are found 

 everywhere. In the little valleys among the hills there is a good growth of grass, 

 and this region has always been the favorite resort of the Bufialo. A species of 

 Yucca [Y. angustifolia) grows abundantly on the sides of the hills, and with its deep 

 branching roots affords a great protection to them from the winds. Water is found in 

 little lakes, which are abundant in the numerous depressions, but they are all very 

 small, and of very little depth. The Miocene beds of the White River present some 

 of the most wonderfully unique scenery in the world. Over an area of about one 

 hundred miles from east to west, and fifty to sixty from north to south, they have 

 been so worn and cut by streams, rains, and other atmospheric agencies, that it 

 forms one continued series of gullies or dry gorges, with here and there isolated peaks 

 and columns looking much like steeples or towers, giving to the whole the appear- 

 ance of the ruins of some ancient city. Through the courtesy of Prof, James Hall, of 

 Albany, N. Y., I am permitted to make use of the accompanying sketch, which was 

 taken on the spot by Mr. F. B. Meek, while visiting that region under the auspices 

 of Professor Hall. The following vertical section of the beds of this basin, although 

 published some years since, is here repeated, from the fact that I have been unable 



