SCIENTIFIC EXPEDITION TO NORTHEASTERN COLORADO 1 47 



Wyoming and Nebraska line, is a series of bluffs facing southward. 

 These are a very striking feature of the landscape/ rising in places as 

 perpendicular cliffs to a height of perhaps 200 feet. Isolated remnants, 

 parts of the cliffs separated by long continued erosion, remain standing 

 in places as imposing towers rising high above the plains. Of these, 

 Pawnee Buttes are striking examples. In these cliffs are exposed the 

 clays and sand-stones of Tertiary age which are so rich in vertebrate 

 remains. From the base of these cliffs the rolling plains slope gently 

 away southward to the Platte River. From the top of the cliffs, the 

 high plains^ extend away to the northward. 



The Tertiary formations bordering the high plains were visited first 

 at Chalk Bluffs,^ near Cheyenne. Though fossil remains are very 

 plenty in these formations at other places, the expedition was unable to 

 find any in this locality. Around the Davis ranch, a few miles east of 

 Gfover, these formations are very rich in vertebrate remains. Here an 

 expedition from the American Museum of Natural History about seven 

 years ago camped for a considerable time and collected much valuable 

 material. Our expedition spent only six days in this region, making 

 collections noted in the following article. A knowledge of the country 

 and of conditions here, and about Pawnee Buttes a few miles farther 

 east, was gained. This knowledge will be of value in future work. 



The climate of the region is an arid one. The amount of rainfall 

 at Pawnee Buttes can only be approximated by comparing records from 

 the nearest stations which are about 50 miles away. At Cheyenne, 

 Wyoming, the mean annual rainfall is 12.20 inches. At Greeley it is 

 11,16 inches. In the Pawnee Buttes region it is probably somewhat 

 greater, possibly 13 inches. This is less than at most places on the 

 eastern plains of the state. The streams in this region are intermittent, ' 

 most of them carrying only storm water. In most localities wells of 

 moderate depth give a fair supply of good water. The meager rainfall 

 supports a growth of grass sufficient to pasture a considerable number of 

 cattle and sheep. Besides grasses the plants are chiefly early-flowering 

 perennial herbs with some late-blooming composites such as species of 

 Artemisia. This growth of vegetation would not be possible with so 



» See Fig. i, Plate I. ' See Fig. 2, Plate I. 3 See Fig. i, Plate II 



