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



niacus strigatus indicates, however, that it is at best only low 

 Transition. 



Biological Cross-section Camp no. 3 (7000 feet). — This camp 

 was made on a small meadow separated from the main stream of 

 Big Creek by a rocky ledge. The meadow was undoubtedly 

 Transition, as Thomomys fuscus fisheri was trapped upon it, and 

 Iris missouriensis was fairly common on nearby slopes. Zono- 

 trichia leucophrys leucophrys was probably nesting in brush in 

 the vicinity. 



Very high Transition, with a touch of Boreal, was represented 

 on a limited area on a north-facing slope on the south side of 

 Big Creek at this altitude. There were several springs in this 

 area, and the verdure grew as luxuriantly as at any locality in 

 the mountains, the thickets being made up of quaking aspens 

 and many water-loving species of plants. In this cool, protected 

 situation both Hylocichla ustulata swainsoni and Zonotrichia 

 leucophrys leucophrys were noted. 



Biological Cross-section Camp no. 4 (8000 feet; see pi. 9, figs. 

 1 and 2). — This camp at the head of Big Creek, at which more 

 time was spent than at any other established, was located at an 

 altitude of approximately 8000 feet, near the source of the south- 

 ernmost of the main feeder streams. Geologically speaking, the 

 glade in which camp was situated was apparently a hanging 

 valley. 



As might be anticipated, the flowering season was found to be 

 later at this altitude than at the lower camps. Vegetation was 

 comparatively abundant. Quaking aspens grew to a height of 

 thirty feet along the creek. Associated with them in the sheltered 

 caiion was the limber pine, which occurred also quite abundantly 

 on the north-facing slope on the south side of the canon, and less 

 commonly on the south-facing slope on the opposite side. Such 

 plants as the following, referable to Transition zone and higher, 

 were found at this locality: Aquilegia truncata, Bibes cereum, 

 Achillaea millefolium lanulosa, Aphyllon fasciculatum, Pent- 

 stemon confertus caeruleo-purpureus, Arnica chamissonis, Iris 

 missouriensis, Aconitum columhianum, Elymus pubiflorus, Sisym- 

 brium canescens, Allium validum, Ceanothus velutinus, Castanop- 

 sis (species not known), and Veratrum calif ornicum. Of the 



