718 MONOGBAPHS OF NORTH AMERICAN UODENTIA. 



and throat pale fulvous. The tail has also the hairs of the lower surface pale 

 yellowish at the base, thru black, broadly tipped with white. These speci- 

 mens, judging from De Saussure's description, are the more common or normal 

 phase of the species. No. 8495, from Nicaragua, is white, except a broad 

 dorsal band, extending from the occiput to the tail, which is intense brownish- 

 black. The hairs of the lower surface of the tail are white at base, then 

 black, broadly tipped with white, giving a wholly pure white surface to the 

 tail throughout. No. 8628, from Costa Rica (about half-grown), lias the 

 whole body pale yellow or yellowish-white, with an indistinct brownish dor- 

 sal band. The hairs of the tail are wholly black at base, broadly tipped 

 with whitish. Two other specimens, from Southern Mexico, are almost 

 wholly black, being only slightly varied with gray above and on the tail. 



This species differs from most other American species in its slenderness, 

 the great length and narrowness of the ears, and the excessive length of the 

 tail, which, with the hairs, is one-fifth to one-fourth longer than the head and 

 body. Dr. Gray's S. dor salts agrees perfectly with the white, black-backed 

 specimen (No. 8495) above described. The Macroxus melania of the same 

 author corresponds with the black phase of this species, and his M. maurus 

 with the black phase which has the under parts more rufous. De Saussure, in 

 his paper on the Mexican Squirrels (as above cited), describes this species 

 as being usually ferrugineous beneath,* but gives the following phases of col- 

 oration under the head of three unnamed varieties: — a, wholly black, with 

 the hairs more or less fulvous at the base; b, blackish, with the ventral sur- 

 face gray, fulvescent, or dusky; c, body wholly black. 



The original description of Wagler refers to a phase with the lower 

 parts strongly rufous. The length is given as 12 inches from the nose to the 

 end of the tail; the tail (vertebra; only ?) as 11.75. Wagner gives the length 

 from nose to base of tail as 12 inches; of the tail-vertebrae 12.09; tail to end 

 of hairs 14.75. 



I am quite confident that the Sciurus nigrescens of Bennett, described 

 in 1833 as "from that part of California that adjoins Mexico", is referable to 

 the dark phase of the present species. The great length of the tail as com- 

 pared with the body f renders it almost certain that it can refer to no other 



*'• Subtus rufo-ferrugiueus, frequenter pilis nigris intemiixlis, meuto uigrescente." — (Bee. H 

 Mag. dcZoot. 1861, p. . r ,.) 



t According to Bennett, head and body 10.50; tail-vertebnr 10.50; tail to end of hairs 14.00 ; or, 

 according to Bachinan's measurements of the saute specimen, head and body 12.37; tail to end of 

 hairs 15.37. 



