()4 NEBRASKA ORNITHOLOGISTS' UNION 



parallel with the course of the Running- Water. Starting near Andrews 

 and extending down to Crawford the White River Canon divides the 

 ridge into two watersheds, the north one being between White River 

 and Hat Creek, and the south one between White River and the Running 

 Water. 



On the north and northeast. Pine Ridge slopes abruptlj^ through 

 numerous deeply cleft and well Avooded canons, into the Hat Creek 

 Basin, some 1300 feet lower. The pine growth in the western portion 

 is confined to the cafions on the northern escarpment, with a few 

 scattering trees in the canons along White and Running Water rivers; 

 but from Fort Robinson east a more or less scattering- growth covers 

 the entire table of the ridge. 



We have here presented two well-marked topographical subdivisions 

 which for the sake of convenience 1 shall call the "Plateau Region" and 

 "Wooded Canon Region." As will be subsequently shown, each of these 

 respective subdivisions might well be considered as a distinct fauna! 

 area, owing to its possession or non-possession of a great many species 

 peculiar to the other. 



Plateau Region. — Enough has already been said to define the boundaries 

 of this region fairly well. Suifice it to say that it forms the top or 

 table of Pine Ridge in its western portion and varies in altitude from 

 5300 feet near the head of Warbonnet Canon to about 4200 near Fort 

 Robinson. In appearance it is a slightly undulating plain, supporting 

 in ordinary- years a rank growth of range grasses, "nigger-w-ool" pre- 

 dominating. 



In the higher portions of this plateau, particularly in the vicinity 

 of Squaw Butte and at the head of Jim Creek, there are frequent 

 outcroppings of the Arikaree formation in the form of bare chalk 

 buttes from five to fifty feet in height. In these buttes are found the 

 peculiar formations commonly called "Devil's Corkscrews," — the 

 Diamonelix of geologists — concerning- the composition of which there 

 has been so much controversy in recent years. 



No trees or shrubs of any kind whatever grow \ipon this high grassy 

 expanse, and in the remarkably clear air which x^revails at this altitude 

 one can plainly see objects at a great distance. Away to the southwest 

 the top of Laramie Peak shows up clearly above the bold outlines of 

 the Rawhide Buttes, while, shifting our gaze to the northward, the 

 Black Hills are veiled in the purple of the distance. Mirages are not 

 uncommon in July. 



Lupimis plattensis, Toioisendki [iramUfiora. several species of Pi^oralea, 

 Astrafialus hyiHxjUjttis and SediDii steiiopctaluni* are among the charac- 

 teristic plants of the jilateau. 



A number of birds find a congenial summer home here, though few 

 in number compared with those found in the wooded creeks and 



*It is interestlag to note that a butterfly, Parnassius smintheus, usually confiued to 

 the b )real fauna of high mountains, and whose larva feeds on Sednm, flies abundantly 

 on the p'ateau in June. 



