Other east African monkeys with a similar type of colouring, which, together with the wholly black west African C. satanas, collectively constitute the subgenus Guereza, may be included under the same title; and the name may be further extended to embrace all the African thumbless monkeys of the genus Colobus.
The members of the subgenus Guereza present a transition from a wholly black animal (C. satanas) to one (C. caudatus) in which the sides of the face are white, and the whole flanks, as well as the tail, clothed with a long fringe of pure white hairs.
Brachypus, we may consider the genus Rhinoceros to commence; these species constituting the subgenus Teleoceras.
(Dicerorhinus) sumatrensis of south-eastern Asia indicates another subgenus, represented in the European Miocene by R.
Next we have the living African species, representing the subgenus Diceros, in which there are two horns but no front teeth.