The White-bellied Duiker is another discovery of Dr. Gray’s, made, as in the case related in the former article, on a specimen obtained from the interior of a stuffed example of _Tragelaphus euryceros_, received from Mr. DuChaillu. We may therefore fairly put down the locality of the specimen as Gaboon, to which district of Western Africa both of Mr. DuChaillu’s great journeys were confined. As in the former case also, the present species was described in the ‘Annals of Natural History’ for 1873, in a supplementary paper to Dr. Gray’s revision of the species of the present genus published in 1871. To what extent, however, the present is different from the allied species must remain uncertain until further specimens have been obtained, which, so far as we are aware, has not yet been the case. The typical example of _Cephalophus leucogaster_ is probably a female and is quite immature, with the milk-molars still in position and the third molar still below the bone, and it is difficult to arrive at a definite conclusion from such a specimen. At the same time, as Thomas has shown in his article on the genus _Cephalophus_, published in 1892, it is not possible, in the present state of our knowledge, to refer the specimen to any described species. The black dorsal band distinguishes it from _C. nigrifrons_ and other preceding species, and the white hams and under surface from all the forms of the next following species--_C. dorsalis_--to which, perhaps, it most closely approximates. On the whole, therefore, we can at present only say that _C. leucogaster_ has been established on a young specimen of a species of which the adult form is not yet known to us. _May, 1895._ [Illustration: THE BOOK OF ANTELOPES. PL. XIX. _Smit lith._ _Hanhart imp._ Fig. 1. The Red-flanked Duiker. CEPHALOPHUS RUFILATUS. Fig. 2. The Bay Duiker. CEPHALOPHUS DORSALIS _Published by R. H. Porter._] 26. THE BAY DUIKER. CEPHALOPHUS DORSALIS, GRAY. [PLATE XIX. FIG. 2.] Subspecies _a_. C. D. TYPICUS.