23 6 I' iiin rsity of California Publications in Zoology [Vol. 10 



hand we have found ourselves unable to establish from our study 

 of the vertebrate animals the presence of more than the lower 

 division of the Boreal, namely, Canadian. Hall, from his study 

 of the plants, recognizes all three divisions of the Boreal zone, 

 namely, Canadian. Hudsonian, and Alpine-Arctic. His argument 

 for the recognition of the last is based, it seems to us rather 

 insufficiently, upon the presence of three species of plants peculiar 

 to this zone. Since no exclusively Hudsonian species are listed 

 by him, his recognition of the Hudsonian zone mast rest on the 

 presumption that if there is Alpine-Arctic, the interlying zone 

 between it and Canadian must be present also. 



In our examination of the vertebrate portion of the biota 

 of the same localities studied by Hall, we have failed to discover 

 any representative of exclusively higher zonal position than Can- 

 adian. Our use of the inclusive term Boreal in dealing with the 

 animals appears to us both safer and more convenient than to 

 use one or more separate designations for the divisions faintly 

 indicated in the flora alone. 



As a further consideration, there would appear to be small 

 reason for the presence of anything above the Hudsonian at 

 farthest. The relatively small area of sufficiently high altitude 

 to brine- even Hudsonian conditions might in itself be the cause 

 of the absence of the requisite low temperature for the two higher 

 /ones, save in extremely limited spaces in the north-facing gulch 

 .it the head of Snow Creek, where snow banks linger nearly 

 through summer. It was here that Hall found the three Alpine- 

 Arctic plants. 



A law is probably indicated in this and similar cases, that 

 the sharper an isolated peak, that is, the more abrupt the flank- 

 ing slopes, the higher extend the low zones; or, expressing the 

 idea reversely, the larger the land mass of high altitude the lower 

 extend the high zones. In the vicinity of Mount "Whitney. 200 

 miles to the north of San Jacinto, the Canadian zone runs up 

 to an average of 9000 feet, the Hudsonian to 11.200 feet. The 

 highest point on San Jacinto is 10,800. 



Thus altitude, latitude, and the above law all argue against 

 the existence of zonal conditions on San Jacinto much higher 

 than Canadian. The animal life certainly indicates this as far 



