KUNGL. SV. VET. AKADBMIENS HANDLINaAR. BAND 48. N;0 5. 



35 



Among the differences between this species and G. albotorquatus, Neumann^ 

 mentions the »red anal region* of the latter. In consequence of this Pocock^ states 

 that in skins from »the Kedong» Escarpment » (probable the same as the present 

 Escarpment railroad station), and such from Boromo »a considerable quantity of 

 brownish red hair* is to be found at the sides of the ischial callosities, while in spe- 

 cimens from Nairobi this is less well developed. Pocock appears therefore to be in 

 doubt whether »more than one species is here involved », The present material 

 appears to throw light on this question. In four fine old males from the forest at 

 Escarpment station the red of the ischial and anal regions is absent except in the 

 specimen with the shortest canines and smallest skull which thus may be assumed 

 to be the youngest, although it is fully adult. In a younger female from the same 

 locality the red is well developed in the region mentioned. The same is the case 

 with all the specimens from Nairobi, although it is least abundant in the two oldest 

 females, and best developed in a quite young animal in which the first molar has 

 not yet appeared. In this latter the red hair of the anal region extend even to 

 the root of the tail. To judge from these facts the presence of red hair in the 

 anal and ischial regions of this species evidently is a juvenile charasteristic which, 

 more or less completely, is lost during the ontogenetic development when the animals 

 reach full maturity or old age. This accounts for the seeming irregularity in its 

 development. There is also very Httle probability that two allied species of Cercopi- 

 thecus should live the one at Escarpment and on Kenia, and the other in the forests 

 near Nairobi. 



There is a great difference in size between males and females of this species. 

 This may be seen from the following measurements: 



Adult male from Escarpment 



female from Nairobi 



Greatest 

 length 



116 mm. 



115 » 



114 » 



99 » 



98 » 



97 » 



Basicranial 

 length 



88,5 mm. 

 79,0 » 

 82,0 J 

 70,8 » 

 70,0 » 

 68,0 » 



Condylobasal 

 length 



95,5 mm. 

 95,0 » 

 92,0 » 



77.3 » 

 77,0 » 



76.4 » 



DoLLMAN has named a female specimen from Nairobi Gercopithecus holhi nubi- 

 lus.^ This is said to be distinguished by its »much duller colour of the dorsal sur- 

 face lighter under parts, and less conspicuous white collar*. All these characteristics 

 are rather variable. I have in this collection specimens from Nairobi which are just 

 as bright in their colours as specimens from Escarpment and Kenia which, however, 

 as living at a higher altitude have a somewhat thicker and longer fur. Some of the 



1 Proc. Zool. Soc. London 1902 Vol. II pi. 1 p. 144. 



2 Proc. Zool. Soc. London 1907 p. 703. 



3 Ann. & Mag. Nat. Hist. Ser. 8. Vol. V. 1910 p. 202. 



