Dimensions:--♀ (not fully adult). Height at withers 15 inches, ear 1·8, hind foot 6·7. Skull: basal length (c.) 5·5 inches, greatest breadth 3·2, orbit to muzzle 3. _Hab._ West Africa, from Sierra Leone to the Gold Coast, replaced in the Cameroons by _C. d. castaneus_. Subspecies _b_. C. D. CASTANEUS. Rather larger than _C. d. typicus_, and ears apparently rather longer. Colour deep chestnut all over, the dorsal line deep black, the metacarpals and metatarsals brown. Superciliary stripe chestnut, indistinct, far less bright than in _C. d. typicus_, and the general colour of the head darker and duller. Skull with the muzzle of the ordinary slender elongate shape, the distance from the anterior edge of the orbit to the muzzle exceeding the zygomatic breadth. Teeth decidedly larger than in the typical form. Dimensions of the type, an immature female:--Height at withers 19 inches, ear 2·4, hind foot 8. Skull: basal length (c.) 6 inches, greatest breadth 3·3, orbit to muzzle 3·5. This subspecies is based on a female specimen referred by Gray[13] to “_Cephalophus badius_”; its skull has been figured by him under that name. Thomas has, however, shown that the skull of this specimen differs so much from that of typical _C. dorsalis_ that, in spite of its external resemblance, it should be looked upon as representing a distinct subspecies; and this view we have accepted in the present work. Additional specimens will, however, be needed before its position can be satisfactorily determined. For the present, therefore, we publish all that is known about it, and trust that further specimens from different localities will clear up the precise relationship it bears to the true _C. dorsalis_, and also to its close ally _C. leucogaster_. _Hab._ Cameroons. The Bay Duiker, as this Antelope has long been called, is better known than the species which we have last spoken of and appears to have a wider distribution. At the same time it varies a good deal in the colour of its fur, both according to age and in the various localities in which it is found. Gray, who was an habitual species-maker, has, as was pointed out by Sclater in 1869, described it under three different names, based on age-changes and on slight variations in colour.