282 Mr. E. L Pocock on 



In tlie speckling of the coat and the appearance and 

 gradual extension of the yellow of the underside a gradation 

 may be traced in the order named between C. fuliginosus, 

 Tlagenlecki, agilis, and chr ijsog aster j whereas in the direction 

 of growth of the hairs on the head C. chrysogaster resembles 

 C.fuliginosus. 



G. Agile Mangabey. 



Cercocehus agilis, A. Riviere. 



Cercocehus ac/ilis, A. Riviere, Rev. Sc. s^r. 3, xii. p. 15 (1886) ; Pou- 

 sargues, Ami. Sci. Nat., Zool. (8) iii. pp. 229-235 (1896) ; Trouessart^ 

 Le Natui-aliste, 1897, p. 9. 



Log. French Congo : confluence of the Oubangui and the 

 Congo ; " Poste des Ouaddas" (according to Pousargues). 



The specimen, now in the Paris ]\Iuseuni, to which Riviere 

 gave the name Cercocehus agilis, without adequate diagnosis, 

 was subsequently described by both Pousargues and 

 Trouessart. I have not seen any specimen which exactly 

 fits the descriptions, though the latter apply pretty closely to 

 niangabeys we commonly receive from the Congo and call 

 C. Hagenbechi. The arrangement of the hairs on the fore- 

 head is the same and the speckling of the fur also, but the 

 general tint is apparently different in the two ; for example, 

 Trouessart says that the hairs of the head and back are more 

 distinctly annulated than those of the sides, so that the tint 

 passes insensibly into fawn-brown (*' fauve-brun '^), then into 

 clear fawn, then into white under the belly. And according 

 to Pousargues the hairs of the u])per parts are dark brown 

 (" brun sombre") and marked on the distal third with two 

 yellowish-green annuli especially distinct upon the head, 

 neck, and arms, much less defined upon the cheek, shoulders, 

 back, sides, and outer face of the legs ; the hairs of the chest 

 and belly are scanty and yellowish red at the extremity, but 

 the throat and the inner sides of the arms and legs are silvery 

 grey. The discrepancies between the two descriptions taken 

 by two authors of repute from the same specimen are difficult 

 to reconcile. They are also highly instructive as emphasizing 

 the magnitude of the personal equation to be reckoned with 

 in judging of species from published diagnoses. The reddish- 

 yellow ("jaune roussatre ■'^) hue of the chest and belly must 

 be very faint, one would imagine, to admit of Trouessart^s 

 failing to detect it and describing the belly as white, unless 

 his examination was made by gas- or candle-light. That 

 Pousargues was probably correct may be inferred from the 

 circumstance that he saw four specimens in addition to the 



