54 T-HE MAMMALS OF ETHIOPIAN AFRICA 



the same district, is similar in colouring but with a greyish mane. From the 

 king guereza, C. angolensis of Angola differs in having the chest and at least 

 the terminal two-thirds of the tail white. The white-thighed guereza (C. vellerosus), 

 on the other hand, is black with a white chin, tail, and thighs ; while the bay 

 guereza (G. ferrugineus), of Gambia and the Gold Coast, is greyish on the crown 

 and upper-parts, and bright reddish brown on the cheeks, throat, under-parts, and 

 limbs. Finally, the light brown crested guereza (G. cristatus) has the white hair 

 of the head long enough to be parted down the middle, that of the forehead 

 radiating from two whorls on the temples. 



The black and the black-and-white guerezas form an interesting instance of 

 the evolution and gradation of colouring. Starting with a wholly black monkey, 

 like the West African G. satanas, in which, although there is a fringe of long hair 

 round the face, the body is comparatively short-haired and the tail not tufted, a 

 gradation can be traced through species like C. palliatus and C. sharper of east 

 central Africa, in which tufts of long white hair (larger in the second than in the 

 first of the two species named) make their appearance on the sides of the face and 

 shoulders, as well as on the terminal third of the tail, to the Abyssinian C. guereza, 

 in which the white shoulder-tufts extend backwards to form a mantle on each side 

 of the body, and uniting on the lower part of the back. The culmination of this 

 type is formed by the white-tailed guereza (G. caudatus) of the Kilimanjaro district, 

 in which the pendent white mantle is still longer, and the tail, which is wholly 

 white except for a small length at the root, is clothed with long drooping hair ; the 

 cheek and throat tufts, however, have been lost, so that the head is short-haired, 

 with the face and throat white. 



The West African white-thighed guereza (0. vellerosus) appears to exhibit a 

 kind of retrograde development in these respects, the body having lost the mantle 

 of loDg white hair and the tail its white " flag," while the white of the perineal 

 patch has spread on to the hinder and outer sides of the thighs. In this case we 

 find practical reversion to the type of the black guereza, with the exception that 

 the band on the forehead, the sides of the face and throat, the thighs, and almost 

 the whole tail have become white, while the long hair has disappeared from the 

 face. Probably the colouring and special development of the long hair in the 

 white-tailed guereza form a protective modification, but the purport of the colour- 

 ing of the intermediate forms between this and the black guereza has not been 

 determined. 



The so-called guenons form another exclusively African genus 

 'of monkeys, with a distribution extending from Gambia and 

 Abyssinia to the northern districts of Cape Colony. These guenons, forming the 

 large genus Cercopithecus, are divisible into a number of groups characterised by 

 certain peculiarities of colouring. The first of these is the spot-nosed group, 

 distinguished by a heart-shaped white spot on the nose, accompanied by a white 

 or greyish white under surface to the body ; the inner sides of the limbs, the lower 

 side of the tail, at least at the base, being also white. Of the various species, the 

 lesser white-nosed guenon (G. petaurista), from the Gold Coast, is very common in 

 captivity, Biittikofer's guenon (0. p. buettikoferi), from Liberia, being a local race 

 lacking the black line which in the first-named species crosses the forehead ancj 



