156 ALLEN’S NATURALIST’S LIBRARY. 
In some species the upper part of the head has a shade of 
yellow, caused by the colour of the lower half of the hairs 
showing through the black tips. 
Distribution.— Bolivia ; Veragua, Central America; and the 
warmer regions of Costa Rica, where it inhabits the humid 
forests. 
Ill. THE COMMON SQUIRREL-MONKEY. CHRYSOTHRIX 
SCIUREA. 
Stmia scturea, Linn., Syst. Nat., 1., p. 43 (1766); Humb., 
Obs. Zool., p. 334 (var. cassiguiarensis). 
Callithrix sciureus, Geoffr., Ann. Mus., xix., p. 113 (1812). 
Saimiri sciureus, Cuv., Reg. An., p. 103, pl. 1 (1829) ; Schl., 
Mus. Pays Bas, vii., p. 242 (1876). 
Chrysothrix lunulata, Geoffr., Arch. Mus., iv., p. 18 (1844). 
Chrysothrix scturea, Wagner in Schreb., Saéugth. Suppl., v., 
p. 120, pl. 9, (1855) ; Gray, Cat. Monkeys Brit. Mus., p. 
5241070) > Sclater, PZ. 5., 1846, p.. 305- 
Chrysothrix nigrivittata, Wagn., Abh. bay. Ak. Miinchen, 
¥., Dp. 40T: 
Characters——Smaller than the two preceding species ; face 
greyish-white ; chin round and prominent; head blackish- 
grey ; back grey, or grey washed with gold, the basal part of 
the hairs golden and the tips black ; outer side of the fore-arm 
yellow ; tail long, slender, grizzled grey, with the tip black. 
Length of the body, 10 inches; of the tail, 14 inches. 
‘Certain females, examined by Dr. Sclater, had a distinct 
black line along the side of the crown above each ear and ex- 
tending in front, down the side of the face, nearly to a level 
