270 Bulletin American Museum of Natural History. [Vol. XXXIV, 
three fourths of the hairs black, the apical fourth orange; under surface of 
tail at extreme base grizzled rufous and black, beyond the basal inch black 
to the tip, broadly fringed for the distal two thirds with orange, includ- 
ing the terminal hairs. | : 
Total length (No. 19672 Field Mus., 2 ad., Yurimaguas, Peru), 533 mm.; 
head and body, 273; tail vertebree, 260; hind foot, 69. Skull (same speci- 
men), total length, 69; zygomatic breadth, 38.7; interorbital breadth, 21; 
postorbital breadth, 19; breadth of braincase, 24; nasals, 22 8; diastema, 
21; maxillary toothrow, 10. Another specimen (No. 19673 Field Mus., 
2 ad., Lagunas, Peru), total length, 70.3; zygomatic breadth, 39.3; inter- 
orbital breadth, 21; postorbital breadth, 20; breadth of braincase, 24; 
nasals, 20.5 X 10; diastema, 21; maxillary toothrow, 10. | 
Specumens examined, 3.— Peru: Yurimaguas, 1, and Lagunas, 1 (Field 
Mus.); Rio Madre de Dios, 1 (Mus. Comp. Zoél.). 
Remarks.— In common with the other large squirrels of South America 
Scvurus tricolor presents a wide range of individual variation, especially in 
the color of the ventral surface, which in some specimens is deep rufous, in 
others yellowish white or nearly clear white. SS. tricolor differs from the 
large squirrels of the langsdorffit-igniventris-pyrrhonotus group in the form 
of the skull, which is relatively longer and narrower, with a relatively 
longer and narrower rostrum, a longer diastema, and longer lower incisors. 
Urosciurus duida (Allen). 
Text Fig. 11 (p. 164); Plate X, Figs. 4-6; Plate XIV, Figs. 1, 2. 
Sciurus duida ALLEN, Bull. Amer. Mus. Nat. Hist., XX XIII, p. 594, Oct. 8, 1914. 
T'ype locality.— Rio Cunucunumé, southern base of Mount Duida, 
Venezuela; altitude 700 feet. | 
Geographic distribution.— Known only from the type locality. 
Description.— “ Size large, pelage long and soft with abundant underfur: 
tail very broad. Upperparts (type) blackish washed lightly with pale 
cream color, the hairs brownish black slightly tipped with cream color, the 
general surface effect yellowish gray on a brownish black ground color 
top of head darker brown, the hairs minutely tipped with pale rufous; sides 
of head cinnamon brown; lower back and rump scarcely darker than the 
middle of the back but the hairs are tipped with very pale rufous instead of 
cream color; underparts dark ferruginous to the base, the upper chest and 
throat paler; fore limbs and feet intense deep rufous; hind limbs externally 
chestnut grizzled with black, internally dark ferruginous; upper surface 
of hind feet reddish orange; tail above black for about the basal fifth, rest 
