332 University of California Publications in Zoology. [Vol. 7 



One fact of distribution may be of particular interest, 

 namely, the occurrence on Alder Creek not far above the ranch 

 of a Populus, tentatively identified by Professor H. M. Hall of 

 the University of California as P. balsamifera. The species was 

 represented by a clump of four trees only. The tree is northern 

 in distribution, the nearest locality from which it is reported by 

 Sudworth (1908, p. 244) being northern Oregon and Idaho. 

 May not a colony of these trees have been left here when the 

 cooler environment of the Glacial period retreated? 



Zonally Alder Creek Ranch (Camp no. 8) is referable to 

 Upper Sonoran. Ammospermophilus leucurus, Neotoma nevad- 

 ensis, Phrynosoma platyrhinos, Tyrannus verticalis, and Icterus 

 bullocki were all recorded here. That it is high Upper Sonoran 

 is shown by the fact that the green-tailed towhee occurs in the 

 neighborhood. The apparent absence from Alder Creek Ranch 

 of CiteUus mollis, so abundant on the other side of the mountain, 

 and the scarcity on the Alder Creek side of Centrocercus uro- 

 phasianus, common on the Big Creek side, and so very numerous 

 on the Leonard Creek flats, attracted our attention. Possibly 

 these facts are accounted for, the first on the theory that Alder 

 Creek Ranch is higher in Upper Sonoran zone than is the Quinn 

 River Crossing district, and the second on the observed fact that 

 the sage-brush was very much more sparse on the Alder Creek 

 slopes than on Big or Leonard creeks. 



Leonard Creek (6000 feet). — The flats and mesas drained by 

 Leonard Creek are by far the most extensive in the mountains. 

 The main ridge rises up to the west of the Leonard Creek basin, 

 furnishing several tributary streams, while toward the east 

 appear the Pine Forest foothills culminating in Sentinel Peak 

 (6800 feet), and presenting a very arid and barren appearance 

 indeed. 



Except where interrupted by patches of dry meadow the flats 

 were covered with sagebrush, which was locally very luxuriant. 

 These dry meadows were apparently slightly more favorably 

 situated as regards moisture conditions than the rest of the flats ; 

 the most conspicuous members of their flora were grasses and 

 Iris missouriensis. 



Willows were the dominant trees along the stream. A few 



