708 MR. R. I. POCOCK — A REVISION OF [June 18, 



«iid of the tail of this species distinguishes it at once from the 

 rest of the species of the Albogularis-section. The uniformity 

 in the tint of the speckling of the dorsal surface from the head to 

 the root of the tail is another distinctive feature. 



The MONA-group. 



Mona Reich. ; Mona + Otopithecus Trouess. 



Pale colour of inner side of arms sharply contrasted, especially 

 along the radial aspect, with the black or dark grey tint of the 

 outer side. A black temple-band extending from eye to ear and 

 sharply separating the colour of the cheek from that of the 

 summit of the head. A well-defined pale brow-band, which some- 

 times extends over a large part of the summit of the head. Face 

 slate-blue, but median area of lips flesh-coloured. Shoulder and 

 anterior portion of back redder or greyer than the posterior area, 

 which tends to turn black. 



Distr. From Sierra Leone through the Gold Coast, Nigeria, 

 and the Congo to the Ituri Forest. 



Key to the Species and Subspecies. 



a. Ventral surface at least laterallj^ and at least the margins of 



the limbs suffused with rustj^ yellow ; hairs on ears rustj^ 



yellow. 



h. Outer side of hind limb from hip to ankle rusty, the color^rs 



of the thigh and sacral area sharply defined; throat and 



chest white ; red on the belly and on the inner side of the 



limbs pronounced only whei'e the white passes into the 



coloured outer or lateral surface wolfi. 



b'. Outer side of hind limb usually greyish, sometimes suffused 

 with yellow, but the colours of the thigh and sacral areas 

 not sharply defined from each other; the entire ventral 

 surface (at least in the adult) yellowish or rusty red. 

 c. Arms externally speckled, not black ; a jet-black band con- 

 siderably moie than twice as long as broad and sharpljr 

 defined laterally from the greyish lateral surface extend- 

 ing from behind the shoulders to the rump ; no distinct 



double or U-shaped pale mark on the head pogonias. 



c'. Arms black; a black patch on lumbo-sacral area, if 

 present, not sharply defined laterally and not twice as 

 long as broad ; a decided U-shaped pale patch on the head, grayi. 



d. Lumbo-sacral area of dorsal surface jet-black Subsp. nigripes. 



d'. Lumbo-sacral area usually reddish, speckled : sacral 



area sometimes jet-black Subsp. grayi. 



a' . Ventral surface, throat, and inside of limbs white at all 

 ages; hairs on ears usually speckled. 

 e. A conspicuous white patch on each side near the root 



of the tail mona. 



e'. No white patch near root of tail. 

 f. Outer surface of hind legs and more or less of the lumbo- 

 sacral area black or dark grey and scarcely speckled, 

 contrasting with the fore part of the dorsal surface. 

 g. Brow-patch white and cheeks and side of neck pale 

 greyish, gradually passing into the white of the throat, 



as in C. mona ; hairs on ear speckled camphelli. 



g'. Brow-patch yellow usually, ill-defined, but spreading 

 backwards over forehead ; cheeks and side of neck dark 

 dusky greyish green, sharply defined h'om white of 



throat ; hairs on ear yellowish burnetti.. 



/'. Outer surface of hind legs and the lumbo-sacral area 

 much the same colour as the fore part of the dorsal 

 surface — that is to say, speckled red and black denti. 



