206 Bulletin American Museum of Natural History. [Vol. XX, 



with reddish, chiefly below the surface and only slightly visible, instead 

 of dark rufous or reddish chestnut along the back from shoulders to 

 rump, as in typical durangi; sides of nose (to eyes) gray, in some 

 specimens faintly tinged with pale buff, not "dingy gray suffused with 

 brownish but usually reddish brown," as in durangi; eyering soiled 

 white ; base of ears externally pale reddish brown ; a prominent black 

 lateral line; tail gray above and below, more finely grizzled below, 

 broadly fringed with white, exactly as in durangi. 



Measurements. Type: Total length, 493 mm.; head and body, 271 ; 

 tail vertebra, 222; hind foot, 69. A series of n adults measure: 

 Total length, 477 (453-508); tail vertebrae, 216 (203-229). These 

 measurements are considerably below those given for S. durangi by 

 Mr. Nelson (Proc. Washington Acad. Sci., I, 1899, p. 86). 



This subspecies is based on 12 specimens collected at La 

 Cienega (alt. 7000 ft.) and Cienega Corrales (alt. 7000 ft.), 

 Nov. 1-13, and hence in fall pelage, with the ear-tufts only 

 slightly developed. The series is very uniform in coloration. 

 The faint reddish suffusion of the back is mostly hidden below 

 the surface, giving the effect of dull gray with a faint reddish 

 cast, scarcely noticeable except on close inspection. A single 

 specimen forms an exception, having the whole middorsal 

 region strongly reddish, but much less red than typical 

 durangi. 



Sciurus aberti ph&urus differs from S. aberti durangi mainly 

 in the absence of the reddish brown dorsal area and in smaller 

 size. As regards coloration, it is almost the exact counterpart 

 of 5. aberti ferreus of True (described originally as 5. a. con- 

 .color) from northeastern Colorado, the most distant point 

 from Durango in the range of the Sciurus aberti group. 



Since writing the above I have had an opportunity, through 

 the kindness of Dr. C. Hart Merriam, Chief of the Biological 

 Survey, to examine the fine series of Sciurus durangi collected 

 by Messrs. E. W. Nelson and E. A. Goldman, comprising a 

 series of 24 specimens, all practically topotypes of the species. 

 These are all red-backed, in striking contrast with the form 

 here named ph&urus. Seven specimens in the same collection 

 from Guadalupe y Calvo, Sonora, are variously intermediate 

 between aberti, durangi, and ph&urus; three of them are dis- 



