PHYSICAS E NATURAES 97 



The above differences are larger and of easer apprecialion than 

 those separating other forms accepted as well defined species by the 

 most particular authors. Leaving quotations aside, I point out the two 

 congenerous: — the C. nictitans, Erxleben, and the C. melanogenys, 

 Gray, accepted by Schlegel. These two species only diíTer «par sa (C. 

 melanogenys) poitrine et le dedans de son avant bras blancbâtres tem- 

 ais que cette teinte tirant un peu au grisátre oceupe également le ventre 

 jusque sur la base des cuíssqs (Schl. 1. c., p. 90)». It seems to me, 

 contrary to Schlegel, that this difference does not separate them «d'une 

 manière tranchée», principally because it exists between the two spe- 

 cies the C. martinii, Waterhouse, considered by Schlegel as a variety 

 of the C. nictitans, which still more reduce the above difference, as in 

 the C. martinii «la teinle dominante est moin foncée et tirant au gri- 

 sátre notament sur le dessous ...» 



The tail's colour, so steady and unvarying, separatey perfectly the 

 three forms I speak of, and, together with the olher characteristies, au- 

 thorize me lo consider them different species. 



This group of the Cercopithecus wilh a white spot on the nose 

 may be ihen defined as follows: 



Basis of the triangle for med by the white hairs that covered a part 

 of the nose turued upwards : 



I) Face not blue C. petaurista 



II) Face blue. .* Erxleben 



1) Tail olivaceous or olivaceous on the 

 upperside, and white on the under- 

 side turning reddish yellow un the 

 extremity C. ascanias 



Audebert 



2) Underside of basis of tail dark 

 reddish brown and end blackish.. C. ludio 



Gray 



Schlegel (1. c, p. 86) says: aJoues teintes de blanc sur une étendue plus ou 

 moins grande». According the Audebert the tail is ((olivâtrei>, according the 

 Schlegel «le blanc du dessous de la queue change dès le deuxième de la lon- 

 gueur de cet organe au roux rougeatre» , and according the Gray «. . .end of 

 the tail blackish» . . . «and underside of bases of tail dark redJish brown*. 



