1()4 Mcrr'mni New Chipmunks from Colorado nml Arizona. 



mountain species is slightly smaller than the foot-hills form, 

 but the name qwidrivittotiui ' J has heen commonly applied to 

 both. Say's original description is equally applicable to both, 

 except for the measurements, which were given as follows : 



" Length from the nose to the base of the tail, 1] inches, 

 of the tail, :> 



of the hair at tip of the tail, 1 nearly." 



As we measure mammals nowadays, Say's measurements of 

 body and tail are too small for even the smaller of the two 

 species, but it must be remembered that at the time Say wrote, 

 and for half a century afterwards, no rules for the measurement 

 of mammals had been formulated, and that by the 1 old method 

 the -dimensions recorded were 1 considerably less than by present 

 methods. Furthermore, the difference in size of the two species 

 is so slight that the fact that there are two species in the 

 region appears to have thus far escaped the attention of 

 naturalists. The third measurement given by Say, that *jf the 

 length of hair at tip of tail, agrees best with the larger species 

 the tail hairs of the smaller one, particularly in worn summer 

 pelage, falling considerably short of an inch. 



Field work conducted in Colorado by several field naturalists 

 of the Biological Survey (E. A. Preble, J. Alden Luring, and 

 Vernon Bailey) has demonstrated the fact that the larger of the 

 two chipmunks is common throughout the Arkansas Valley in 

 the region at which the type specimen was obtained, and that 

 the small mountain species does not occur in the 1 region at all 

 and can not be found until the mountains are penetrated far 

 enough to reach the Boreal /one. This shows beyond question 

 that Say's quadrivittatm is the foot-hill chipmunk of eastern 

 Colorado, and that the mountain species, which has commonly 

 been included under this name, requires a new name. 



Comparison of the Colorado mountain chipmunk with the 

 other small chipmunks of the West shows that its nearest rel 

 ative is E. <finii',nus of the California Sierra, thus affording another 

 instance of the close relationship of species inhabiting the moun 

 tains bordering the two sides of the Great Basin. 



Eutamias amoenus operarius subsp. uov. 



Type, from Gold Hill (altitude 7,400 feet), Colorado. No. 129,808, 9 young 

 adult, U. S. National Museum, Biological Survey Collection. October 8, 

 1903. Vernon Bailey. Original No. 8160. 



