MAMMALS OF THE MEXICAN BOUNDAEY. 279 



External measurements.— Length, 530 mm.; tail vertebrae, 250; 

 tail to end of hairs, 330; ear from crown, 23; ear froni notch, 33; 

 head, 70 ; hind foot, 75. 



Rernarks.— It is my .good fortune to have at my disposal, in addi- 

 tion to the thirty-five specimens of the two forms of this species col- 

 lected by myself, the series belonging to the U. S. National and 

 American museums, aggregating a much larger number than it has 

 hitherto been possible to bring together. Careful comparisons of this 

 material have developed the interesting fact that this species, like 

 Sciurus rarolinensis, undergoes a marked seasonal change of pelage, 

 the upper surface having an almost uniformly gray coloration in 

 summer, but with a distinct dorsal stripe of fulvous in winter. The 

 feet appear to be grayish at all season unless stained." 



The subspecies huaehuca of Allen was based on four specimens, 

 all adult (two males and two females), from the, Huaehuca Moun- 

 tains, Arizona, taken January 28 to February 20 by Messrs. Price 

 and Condit. They were compared with four specimens taken at Hassa- 

 yampa, near the type-locality of Sciurus arisonensis Coues, during 

 the first week of January. The four Hassayampa specimens have 

 the fulvous dorsal area continuous from the crown to the root of the 

 tail. Doctor Allen's four specimens from the Huaehuca Mountains, 

 ( aken at about the same season and also in winter pelage, have much . 

 less fulvous on the dorsal surface and also a paler fulvous coloration 

 of the under surface of the tail and a reduction in the amount of ful- 

 vous at the base of the hairs of its upper surface. 



As this squirrel loves to feed upon the walnut {Juglans rupestris) , 

 and often eats the immature nut, its pelage during July and August 

 is commonly stained with the juice. The white hair of the under 

 surface becomes tawny-ochraceous wherever the walnut juice comes 

 in contact with it, and toward the end of the season those that feed 

 habitually on the walnut become almost uniformly of this color on 

 the whole under surface. The naked palms and soles are likewise 

 stained. Such individuals have much the cqloration of fox squirrels, 

 and the staining has the appearance of a natural hair coloring. 

 In speaking of such a specimen (No. 11146, U.S.N.M., collected in- 

 Arizona), Doctor Allen observes that it " has the lower surface con- 

 siderably varied with irregular patches and streaks of pale yellowish- 

 rufous, thus showing a tendency to the acquisition of a rufous belly, 

 no common a feature among the squirrels of Mexico and Central and 

 South "America." Comparing this specimen with those of my collec- 

 tion known to have the pelage stained by walnuts, the shade of color 

 is seen to be almost precisely the same; and around the nipples 



«■ In the eastern gray squirrel (Sciurus caroUnensis) the corresponding sea- 

 sonal difference is accentuated by the different coloration of the feet, which are 

 rusty fulvous in summer and grayish white in winter. 



