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



suffusion of reddish brown, they agreeing in this respect with 

 typical ph&urus, but the lower surface of the tail is lightly 

 washed with white instead of being wholly grizzled gray. I 

 have since had the pleasure of examining a series of 2 2 speci- 

 mens in the collection of the Biological Survey, from Colonia 

 Garcia and vicinity, of which about half have the dorsal 

 region gray, while most of the others have the reddish brown 

 dorsal area common to true S. aberti and 5. aberti durangi; 

 all, however, have the under surface of the tail superficially 

 white not solidly white as in true aberti. The red-backed 

 specimens are strikingly similar to the Sonoran red-backed 

 Guadalupe y Calvo specimens noted above under 5. a. phceurus 

 as intergrades between 5. aberti and S. a. durangi, and per- 

 haps they should be considered as intergrades between the 

 form here described as barberi and aberti. The color of the 

 feet varies with season in probably all the forms .of the aberti 

 group, being gray in summer and white in winter, but the 

 amount of white on the feet is to some extent correlated with 

 the color of the under surface of the tail. 



Sciurus aberti forms a curiously variable group, with some- 

 what parallel lines of variation in widely separated localities, 

 the intermediate regions being occupied by other and very 

 different forms, as illustrated by the distribution of 5. a. ferreus 

 and 5. a. ph&urus, in comparison with that of true aberti. 



* 4. Eutamias canescens, sp. nov. 



Type, No. 23852, Am. Mus. Nat. Hist., ? ad., Guanacevi (alt. 

 8000 ft.), Durango, Mexico, Oct. 12, 1903; coll. J. H. Batty. 



Similar in general appearance to E. dorsalis, but with the dorsal 

 stripes much more strongly denned. General color above gray, suf- 

 fused with fulvous, the tips of the hairs being whitish with a subapical 

 zone of yellowish, which more or less tinges the surface ; median dorsal 

 stripe narrow, deep black, extending from middle of crown to base of 

 tail; the two lateral dark dorsal stripes short, mixed fulvous, gray and 

 black, the black sometimes predominating but usually obscured by the 

 gray and fulvous; inner pair of light stripes ashy gray, the outer 

 lighter, whitish gray, sides pale rusty fulvous, much brighter than in 

 E. dorsalis; tail as in dorsalis, above mixed gray and black, sides 

 fringed with whitish gray, lower surface with the central area and 



