528 Mr. E. Schwarz on 



these latter were white, as seen from the full description as 

 well as from the photograph in the text. 



It is quite obvious that all these monkeys present different 

 stages or' albinism of the same species, G. aterrimus, first 

 described by Oudemans in 1890. The original description is 

 excellent, and points out all the differences which separate it 

 from C. albigena, together with a female of which the type 

 specimen was received at the Zoological Gardens, the Hague. 



The differences are : C. albigena has soft dull black hair 

 and a mantle on the shoulders, while in G. aterrimus the fur 

 is coarse, glossy black, and the mantle is absent. There \i 

 also present a long brow-fringe in G. albigena, but not in 

 C. aterrimus. Tlie cheeks of C. albigena are quite short- 

 haired, whereas G. aterrimus possesses long greyish-brown 

 whiskers partly concealing the ears. In C. albigena the 

 crest is occipital in position and broad behind ; in C. ater- 

 rimus the crest is quite vertical in the centre of the crown 

 and pointed. 



It so happens that this same species (C. aterrimus) has 

 had bestowed upon it another name. When making some 

 remarks on C. albigena (Nov. Zool. vol. vii. 1900) Mr. Ly- 

 dekker mistook the description of C. aterrimus, which he 

 referred to a monkey in the British Museum belonging to 

 G. albigena albigena, as will be shown below. This monkey 

 has a distinct brow-fringe, no whiskers, a mantle, and an 

 occipital crest, while the monkey he described and figured as 

 C. albigena rothschildi undoubtedly is the same as G. ater- 

 rimus of Oudemans, having no mane nor superciliary fringe, 

 being black all over except the long greyish-brown whiskers, 

 and having the characteristic peak-shaped crest on the crown 

 found in C. aterrimus. The British Museum possesses an 

 adult specimen which agrees in all details with G. aterrimus, 

 but which unfortunately has no skull. It was collected by 

 Mr. Simpson at Bena Dibele, Lukenye River, South Central 

 Congo. This is the eighth specimen of this species known to 

 me, but the only one with exact locality. Most probably G. ater- 

 rimus inhabits the large basin south of the Central Congo, the 

 district of the Sankuru River, Lukenye River, &c. The 

 fact that two specimens (the types of both G. aterrimus and 

 C. congicus) were said to be from Stanley Falls only confirms 

 me in this opinion. Possibly Cercocebus aterrimus occurs 

 together with a subspecies of Cercocebus albigena, which is met 

 with from the Cameroons to the Lake District, though it would 

 seem to me that C. albigena and its subspecies live rather 

 north of the Congo and in the Lake District, while the species 



