116 ZOOLOGY. 



sometimes wanting altogether in individuals that at other times possess them. 

 This feature seems to depend mainly upon season, as the tufts are probably 

 shed periodically. The condition of complete melanism has lately been 

 determined to occur in this as in other species of the genus. 



SC1DRUS AEIZONENSIS, Cones. 



Arizona Gray Squirrel. 



Smirus arizonensis, Coues, Am. Nat., i, 18G7. 357 (Fort Whipple, Ariz.).— Ooues, 

 Proc. Acad. Nat, Sci. Phila., 1807, 134. 



"Rather smaller than the eastern Gray Squirrel ; of the same form and body- 

 colors; the tail longer, fuller, and much broader. Ears moderate, untufted, both sides 

 birred. Palm 5-tuberculated, nearly naked, but a little hairy on the concavities of 

 the fingers; 4th finger longest; 3d nearly equal ; 2d equal to 5th. Soles G-tubercu- 

 lated. naked to the heels, but tuned rather far around on their sides; 4th toe longest; 

 I'd and 3d nearly equal, and but little shorter. Tail to end of vertebrae equaling 

 length of body from nose to root of tail : the hairs projecting 3i inches beyond termi- 

 nal vertebra. Above, from nose to root of tail, a uniform mixture of gray, black, 

 white, and tawny; the latter predominating. On the sides of the body and outside of 

 the limbs, the tawny and black disappear, leaving a clear grizzle of gray and white. 

 Below, from chin to anus, with the inside of the limbs, pure white, very trenchantly 

 defined against the color of the upper parts and sides. Eyelids and cheeks, about the 

 nose, white ; woolly space at base of ears ochraceous white. The tail from above is 

 basally of the same color as outside of thighs, the tawny of the back stopping abruptly 

 at its base; in the rest of its extent it is black, broadly fringed with white, and having 

 white hairs scattered sparsely through its black portion. Viewed from below, the tail 

 is tricolor, being centrally tawny, bordered with black, which is in turn fringed with 

 white. 



"Dimensions. — Nose to anterior cauthus of eye, 1.1 (inches and tenths) ; to root 

 of tail, !l.5; tail to end of vertebrae, 9.5; to end of hairs. 13.00; its width, at broadest 

 part, fully G.00. Height of ear, 0.8. Longest whisker, 3.3. Palm to end of longest 

 linger, with claw, 1.0; from olecranon to ditto, 3.G. Heel to end of longest toe and 

 claw, 2.3 ; greatest width of sole, 0.7." — [Descr. orig.) 



This squirrel was discovered by Dr. Coues at Fort Whipple in 18G5, 

 and the single specimen then procured remains unique. Its characters 

 cannot be reconciled with those of any other United States species known. 

 Mr. Allen, in his late critical studies of this group, does not account for the 

 species, though he writes us that possibly it may be the same as one of the 

 Mexican species. In default, however, of any such identification, we con- 

 tinue to regard it as distinct. 



