1905.] MR. R. LYDEKKER ON GUEREZA MONKEYS. 325 



The following papers were read : — 



1. C?oloiir Evolution in Guereza Monkeys. 

 By R. Lydekker. 



[Received November 7, 1905.] 



(Text-figures 54-58.) 



An interesting example of the progi-essive 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-haii-ed monkeys included in the genus 

 Colobus, and which may be collectively designated Guerezas, 

 although the name " giiereza " refei'S propei'ly only to the north- 

 east Afiican repi'esentative of the group. 



Beginning at one end of the series, we have the Black Guereza 

 {Colobus satanas), of M^est Africa, which, as shown in text-fig. 54, 



Text-fi^. 54. 



Black Gueveza (Colobus satanas). 



is wholly black with tufts of long hair on each side of the 

 face and throat, a pointed crest on the croAvn 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 jxdliatios cottoni, 

 in which the face-tufts, chin, and narrow pendent tufts of long- 

 hair on the shoidders are white, while the terminal half of the 

 tail is grey with a white tip, which shows a slight tendency to 



