2 CERCOPITHECUS PETRONELLAE. 
the front and ending on the centre of the crown, entire 
hinder crown, occiput and hind neck down to the shoulders 
olive-green, speckled with black, each hair being black 
with commonly two broad yellowish rings, of which the 
outer one is subterminal, leaving a long black tip to each 
hair. Whole back from the shoulders to the root of the 
tail, and even extending upon the latter, rich chestnut- 
brown, with black specklings, produced by the black tips 
to each hair. No black on the arms, their outer surface 
being olive-green like crown and hind neck; outer surface 
of legs olive-yellow, faintly speckled with black; no white 
patches on crupper, hands and feet grayish, scarcely tinged 
with olive. Front and sides of anterior crown white, faintly 
speckled with black, the white crown-patches separated by 
the narrow olive-green crest, and bordered on the outside 
by a broad, pure black band, running from the orbits to 
and even below the ears. Long, bushy whiskers below this 
black stripe, and a long tuft of hairs in the ears, pro- 
ceeding far behind the top of the hinder edge of the ear, 
yellowish white. Chin, throat, breast and inner surface of 
arms white, with a yellowish tinge, belly and inner surface 
of legs uniform ochraceous yellow. Tail olive-green on its 
basal half, passing into black on the terminal half and 
becoming pure black at the tip. Skin of face blue, upper 
and lower lip flesh-color, covered with very short white 
hairs, intermixed with sparsely-set long, bristly hairs which, 
like the long hairs of the eyebrows, are black. Skin of the 
whole body underneath the fur light blue. Iris light 
chestnut-brown. 
Length of body from front to root of tail 38 centimeters, 
tail 64, fore-arm from elbow to tip of fingers 17, leg from 
knee to heel 14, foot from heel to tip of toes 12. 
The present species, together with C. pogonias, differs 
from all the other known species of the Mona-group by 
the want of black on the outside of the arms, but C. po- 
gonias is easily distinguished from the present species and 
C. grayi Fraser (C. erelebeni Dahlb. and Puch.) by the 
Notes from the Leyden Museum, Vol. XXXIV. 
