252 



SCIENCE. 



[N. S. Vol. XXIII. No. 581. 



The Hudsonian .species alpinus, now re- 

 stricted to the lofty crest of the southern 

 High Sierra, appeal's to be distantly re- 

 lated to oreoceies of Montana, but has no 

 near Relative. 



Another of the Boreal species, amcenus, 

 ranges northward over the Cascades in 

 Oregon and is only subspeeifically distinct 

 from a form inhabiting the boreal forests 

 of the Roclij' Mountains in Colorado. 



The speciosiis group, it will be remem- 

 bered, is represented in the east California 

 section by two forms (speciosus and iiiyo- 

 ensis), which may be called species or sub- 

 species, as you like— the fact being that 

 they are more closely interrelated than are 

 any of the other forms of the region, al- 

 though intergradation has not been proved. 

 But instead of occupying different faunal 

 zones, as do the other species, they occupy 

 different parts of the same zone — speciosus 

 inhabiting the Boreal slopes of the Sierra, 

 inyoensis the corresponding Boreal crest of 

 the adjacent White Mountains (here sepa- 

 rated from speciosus by the Upper Sonoran 

 and Transition zones of Owens Valley). 

 But where did the speciosus type come 

 from? Investigations carried on by the 

 Biological Survey show that the same spe- 

 cific type still inhabits the iipper slopes of 

 the San Bernardino and San Jacinto Moun- 

 tains in southern California, that a more 

 distantly related form (qitadrivittatus) 

 occupies the Transition zone in Colorado, 

 and that between the two, on an isolated 

 mountain peak rising from the arid deserts 

 of soiithern Nevada, is another species 

 (palmeri), more strongly differentiated in 

 consequence of local peculiarities of en- 

 vironment. These facts show not only 

 that the speciosus-quadrivittatus group is 

 a very old one, but also that its ancestors 

 once inhabited the Great Basin itself. In 

 those days the arid deserts of this region . 

 were in their infancy, and must have been 

 completely bridged liy continuity of conif- 



erous forests, connecting the Sierra and 

 Rocky Mountain areas. 



The Desert Range species, panaminiinus, 

 which occupies the Transition zone on both 

 sides of Owens Valley, occurs south of the 

 White and Inyo mountains in the Coso and 

 Argus mountains, and farther east, in the 

 Panamint, Grapevine, Providence and New 

 York mountains in the desert region of 

 eastern California, and on Mount Magruder 

 in western Nevada. It belongs to a group 

 of which only one other species is known — 

 E. liopiensis, of the high desert mesas of 

 northeastern Arizona, southeastern Utah 

 and southwestern Colorado. In this ease, 

 as in that of two other groups already dis- 

 cussed (the amoemis group and the spe- 

 ciosus-quadrivittatus group) the range of 

 the type comprises localities on both sides 

 of the Great Basin. It appears to be an 

 aberrant offspring of the speciosus-quad-i'i- 

 vittatus group and probably originated 

 from the ancestors of that group in the by- 

 gone days when they inhabited the ancient 

 forests of the Great Basin. 



Eutamias senex appears to have origi- 

 nated in the Siskiyou Mountains, on the 

 boundary between California and Oregon, 

 as an offshoot from the redwood chipmunk, 

 oc/iro(/e?ij/s— which in turn is closely re- 

 lated to toivnsendi of the northwest coast 

 of Oregon and Washington. From the Sis- 

 kiyous, senex ranges north along the Cas- 

 cades nearlj'^ to Mt. Hood, and -south in the 

 Sierra to the latitude of Yosemite Valley. 

 In time it may be expected to push on to 

 the south end of the Boi'ear Sierra in the 

 Mt. Whitney region. E. senex appears to 

 be the parent form, directly or indirectly, 

 of two other species— quadrimaculatus and 

 merriami — whose ranges now occupy con- 

 siderable stretches along the flanks of the 

 Sierra. It seems probable that quadri- 

 maculatus oi'iginated near the north end of 

 its present range and under existing geo- 

 graphic and climatic conditions. While, 



