On Cevcocebus aterrimus and Cercocebus albigena. 527 



long and falciform ; its length is always much greater than 

 the distance from its base to the upper edge of the rostrum 

 (fig. 2). _ 



All the appendages are noticeably more slender in the 

 specimens examined than in specimens of P. bonnieri of 

 similar size. The basal lobe of the antennule (stylocerite) is 

 narrower and more produced forwards than in P.bonnieri, and 

 there is a slight angulation of its anterior edge which seems 

 to be constant in all the specimens examined (fig. 2). The 

 type specimens of Spence Bate's P. falcipes undoubtedly 

 belong to this species. 



The Museum collection includes twenty-five specimens of 

 this species from various localities off the east coast of North 

 America, received from the U.S. National Museum and from 

 the collection of the Rev. Canon Norman. 



LXX1I. — On Cercocebus aterrimus and Cercocebus albigena. 

 By Ernst Schwarz. 



In 1906 Mr. Pocock described a new species of Cercocebus 

 which he called G. hamlyni, and which was said to have 

 come from the Upper Congo (this journal, ser. 7, vol. xviii. 

 1906). This animal still lives at the Zoological Gardens, 

 Regent's Park. It is distinguished by its long whiskers, the 

 peak-shaped sagittal crest, the flesh-coloured naked parts 

 (only a few tan spots in the face), and the light colour, which 

 presents a striking contrast to the dusky coloration of the other 

 members of the genus. When recently visiting the Zoological 

 Gardens at Rotterdam I was greatly astonished to find there 

 two examples of Cercocebus which in external form fully agreed 

 with the specimen living in London, while their colour was 

 entirely different. One of them was glossy black all over, 

 only the very long whiskers being greyish brown, with 

 bl.ick naked parts. The second specimen was quite white, 

 with pinkish naked parts, with only two tan spots between 

 the brown eyes. Both came, as Dr. Biittikofer kindly in- 

 formed mp, from somewhere on the Upper Congo, and were 

 labelled Cercocebus aterrimus, Oudem. A third specimen, 

 fully agreeing with the type of C. hamlyni, lives in the 

 Antwerp Zoological Gardens. I must add that in 1899 

 Dr. Selater described a Cercocebus conglcus from a monkey 

 he had seen at the Antwerp Gardens, which was stated to be 

 from Stanley Fall?, Congo, and which had flesh-coloured 

 naked parts, and was "' remarkable for its prominent crest on 

 the middle of the head and the long hairs on the cheeks " ; 



