742 MONOGRAPHS OF NORTH AMERICAN RODENTIA. 
Macrorus boothie Gray, Ann. and Mag. Nat. Hist. 2d ser. xx, 1867, 424. 
Macrocus nicoyana Gray, Ann. and Mag. Nat. Hist. 3d ser. xx, 1867, 423 (Costa Rica). 
Macroxus colliai Gray, Ann. and Mag. Nat. Hist. 3d ser. xx, 1867, 421 (vars. 1 and 2 only). 
“ Sciurus intermedius VERREAUX” (MS, name?; see Gray, 1. c. 421). 
Sciurus rigidus Peters, Monatsh. Kénigl. Preuss. Akad. Wissensch. zu Berlin, 1863 (1864), 652. 
Speciric cuArs.—Form rather stout; muzzle short and broad; ears rather 
small; tail narrow, rather longer than head and body; pelage full, coarse, and 
long. Length of head and body 12.50; of tail-vertebrae 9.75; of tail to end of 
hairs 12.75. Above, dark brown, mixed with yellowish-gray or black, varied 
with fulvous; often paler on the sides, where there is a tendency, in many 
specimens, to a broad, grayish, sub-lateral band; beneath, deep brownish-red, 
frequently with unsymmetrical patches of pure white. Tail below tricolored, 
centrally rufous, then black, with a border of white; the rufous in the middle 
variable in amount and in tint, sometimes obsolete, sometimes forming a 
broad central band of bright rufous, at other times pale rufous. 
This species is so variable in coloration as to be hard to characterize. 
The above diagnosis indicates a condition intermediate between the extremes, 
as well as apparently the most common phase. Of eighteen Costa Rican 
specimens, about half present a quite uniform style of coloration, while of the 
remainder, no two are very nearly alike. Kleven agree quite nearly in having 
the general color above black, varied more or less with reddish-brown, the 
proportion of the two colors varying with each specimen. The ventral sur- 
face in all, including the inner side of limbs, is dark reddish-orange. The 
pelage above is black at base, with a broad subterminal band of fulvous- or 
rufous-brown, the hairs all broadly tipped with glossy black. The sides of 
the head, nose, and chin are grayish-brown; the ears have a rufous spot at 
the base posteriorly. The hairs of the tail are fulvous (in some specimens 
rufous) at base, ringed with black, then crossed by a broad band of black and 
narrowly tipped with white. The color of the central portion of the lower 
surface varies from fulvous to dark brownish-red. Another specimen (No. 
11410) is similar to these, but has less black above, and the rufous of the 
ventral surface is paler; the tail is rufous centrally near the base and toward 
the tip. No. 11864 has still less black above, and the lower surface is irreg- 
ularly marked with large patches of pure white. The tail is also much more 
broadly edged with white, and the ear-patches are also white, as they are in 
the majority of the specimens before me. No. 9306 differs little from the 
last, except in having rather less black above, and in a tendency to a pale band 
