1905. | MR. R, LYDEKKER ON GUEREZA MONKEYS. 325 
The following papers were read :— 
1. Colour Hyvolution in Guereza Monkeys. 
By R. LyDEKKER. 
[Received November 7, 1905. | 
(Text-figures 54-58.) 
An interesting example of the progressive evolution of 
specialised features in colouring (if we may thus term com-~ 
binations of black and white) is afforded by the black and black- 
and-white African long-haired monkeys included in the genus 
Colobus, and which may be collectively designated Guerezas, 
although the name “ guereza” refers properly only to the north- 
east African representative of the group. 
Beginning at one end of the series, we have the Black Guereza 
(Colobus satanas), of West Africa, which, as shown in text-fig. 54, 
Text-fig. 54. 
Black Guereza (Colobus satanas). 
is wholly black with tufts of long hair on each side of the 
face and throat, a pointed crest on the crown of the head, and 
the long tail short-haired from base to tip. Following on this we 
may take a variety of the Mantled Guereza from East Central 
Africa which I have recently described as Colobus palliatus cottoni, 
in which the face-tufts, chin, and narrow pendent tufts of long 
hair on the shoulders are white, while the terminal half of the 
tail is grey with a white tip, which shows a slight tendency to 
