1907.] MONKEYS OF THE GENUS CERCOPITHECUS. 717 



which is probably its nearest ally, as is sliown pi-incipally by 

 the arched inferior cheek-stripe and the extension of the white 

 of the chin and throat up to the ear forming white whiskers. 

 The differences between tlie species are, however, very marked, 

 especially in the I'edness of the belly, the very conspicuous grey 

 patch on the cheek adjacent to the face, the blackness of the nose 

 until maturity or old age is reached, and the marked difference in 

 colour between the under side of the body and the inside of the 

 limbs in C. erythrogaster. 



The PETAURISTA-group. • ■ 



Rhinostictus Trouess. 



Skin of face round the eyes slate-blue or blackish ; of lips pale 

 bluish grey. Usually, probably always in the adult, a distinct 

 black brow-band continuous with a black band extending across 

 the temple on each side backwai-ds to the ear. Area between the 

 eyes with a strip of black hair, which expands on the nose and is 

 confluent with a large cordate white patch narrowing below 

 between the nostrils and transverse, convex, or mesially emarginate 

 above. Dorsal surface from occiput to tail almost uniformly 

 coloured, black speckled with greyish or reddish yellow. Ventral 

 surface from chin to pubic region white or greyish white, paler 

 on inner than on outer side of limbs ; pale area on inner side of 

 upper arm sharply contrasted with the darkei- tint of the outer 

 side. Lower surface of tail pale, at least in its proximal portion, 

 and sharply defined in coloui- from the upper surface. 



Distr. From Libei-ia and Angola eastwards up the Congo 

 Valley to Uga,nda,. 



Key to the S'pecies and iSahspecies. 



K. White of the throat extending upwards on to the cheek 

 almost to the level of the top of the ear, the hairs growing 

 upwards and backwards, and bordered b}'' an upwardly- 

 arched black stripe running from the upper lip beneath tlie 

 ear ; arms speckled to the wrist petaurisia. 



h. A black band, more or less developed, crossing the hack of 

 the head ; no distinct patch of greyish-yellow hair on the 



cheek below the eye Subsp. fetaiiristu . 



b' . No black band crossing the back of the head; a distinct 



patch of greyish-yellow hair on the cheek below the eye . Subsp. huttikoferi. 



a'. White of the throat not extending up on to the cheek; the 



hairs, at least of the lower portion of the cheek, growing 



downwards and backwards ; arms black to the wrist. 



f. Hairs of the cheek yellowish or whitish and marked oft' 



from those of the throat by a more or less well-defined 



black stripe running straight backwards from the upper 



lip beneath the ear ascanius. 



d. Black stripe crossing the lower portion of the cheek 

 broad and expanding on the face adjacent to the upper 



lip ; hairs on ears red Subsp. ascanum. 



d'. Black stripe crossing lower portion of cheek narrow and 

 fading away towards the corner of the mouth ; hairs on 



ears white Subsp. scIunMH. 



c'. Hairs on the cheeks speckled like those on the top of the 



head ; no inferior stripe on the cheek signatus. 



