18 NOETH AMERICAN FAUNA. [no. 19. 



The fauna of the Yukon Ijasin as a whole is composed of two prin- 

 cipal elements, one containing absolutely circumpolar forms, evidently 

 derived from the north, the other containing- forms which have their 

 center of abundance farther south. This is particularly true of the 

 mammals. Among the genera Ijelonging to the north may be men- 

 tioned Ilan(j>fei\ EvoioniyH, Lenniius, and Dlcrostonyx^ all of which 

 are circumpolar in distri})ution; those from farther south are Mcei^^ 

 Sciuropterus, Etttamias, Peromyscus^ Neotoma^ Fihe/\ and Synajytomys. 

 With the exception of alpine species and a few wide-ranging forms, 

 chiefly carnivores, the variations of which are not sufficiently known 

 to be of use in defining faunal regions, no species of mammals are 

 common to the Yukon region and the Sitkan coast district. From 

 this it seems that all the southern forms which reach the Yukon region 

 have been derived from the interior rather than from the coast. This 

 is also true of the trees and to a great degree of the birds. But, on the 

 other hand, some species of land l)irds are common to the lower Yukon 

 and the Sitkan district while a large intervening area in the interior is 

 uninhabited by them.^ SelasphoruH rufus, Dendrolca townsendi^ and 

 Ilyloclchla aoimlascldw were found on both sides of White Pass, but 

 only rarely and for a very short distance on the interior side. 



PREVIOUS WORK. 



Our knowledge of the natural history of the Yukon region has been 

 derived chiefly from two sources — the members of the Kusso-Ameri- 

 can Telegraph Expedition and the Signal Service officers formerly 

 stationed at St. Michael. The first information was gathered l)y the 

 scientific corps of the Telegraph Expedition of 1865 to 1868. Promi- 

 nent among the members of this corps were Robert Kennicott, Wil- 

 liam H. Dall, and J. T. Rothrock, all of whom secured valual)le speci- 

 mens and information. The notes of Kennicott were not published, 

 owing to his untimely death at Nulato, May 13, 1866, but numerous 

 specimens, particularly from the vicinity of Fort Yukon, are now in the 

 National Museum, a monument to his faithful pioneer work. Among 

 the numerous papers on various subjects relating to Alaska published 

 by Dail are lists of birds and mammals.'^ A list of plants including 

 some records from Fort Yukon was published by Rothrock.^ 



^ One of these species is the varied thrush (Hesperocichla nsevia) which was found 

 in the Lynn Canal district, but not in any numbers in the Yukon Valley above Daw- 

 son. Below Dawson it is quite common along the Yukon and undoubtedly breeds 

 there. It is well known to range along the Pacific coast to Kadiak, and thence to the 

 shores of Kotzebue Sound and up the Kowak River. Its absence on the Upper 

 Yukon and its occurrence all along the coast make it extremely probable that in 

 reaching the Yukon its course of migration is up the river from its mouth. 



^ List of Birds of Alaska, by W. H. Dall and H. M. Bannister < Trans. Chicago Acad- 

 emy of Sciences, I, pt. II, 267-310, 1869; also Alaska and its Resources, by W. H. 

 Dall, Boston, Lee & Shepard, 1870. 



^Sketch of the Flora of Alaska, by J. T. Rothrock < Annual Report Smithsonian 

 Institution, 1867, 433-463. 



