Although, as already stated, originally discovered in Sierra Leone, the Yellow-backed Duiker seems to have a somewhat extended distribution along the western coast of Africa, reaching altogether from Liberia to the Congo. A pair of mounted specimens and a skeleton in the British Museum were transmitted from Fantee by the native collector Aubinn. The same collection also contains skins from Lagos, procured by Sir Alfred Moloney, and two skulls and a skin from Gaboon, brought to England by Mr. DuChaillu on his return from his celebrated gorilla-hunting expedition. Upon one of these skulls in 1865, Dr. Gray established his _Cephalophus longiceps_, and upon the second skull and the skin which accompanied it, in 1871, the same author based his _C. melanoprymnus_. Thomas has shown (P. Z. S. 1892, p. 416) that both these names are merely synonyms of, _C. sylmcultrix_[12]. We may add we have as yet no information as to the range of this species into the interior, except that Herr Matschie has recorded its occurrence in Togoland; but it must be explained that our knowledge of the distribution of West-African mammals is still woefully deficient. As the same gentleman informs us, there is, besides several skins from Togoland, a stuffed example in the Berlin Museum sent by Herr Pechuel-Loesche from Longobondo. Our illustration of this species on Plate XIII. is copied from a watercolour drawing taken in April 1894 by Keulemans, from a fine male specimen living in the Zoological Gardens of Rotterdam. As this animal was received from the Congo in June 1891 (presented by Heer A. de Bloeme) it must be necessarily quite adult. Mr. Keulemans’ notes on it are as follows:--“Head dark grey; neck grey, shading into brownish and becoming blackish near the shoulders; hairs of neck and head very short and glossy; general colour dark brown, with a bluish gloss, getting blacker on the buttocks, where the hairs are long; tail short and black; large plaque on the back and buttocks and tuft between the horns brownish ochre.” Our second figure (Plate XIV. fig. 2), which was prepared by Mr. Smit under Sir Victor Brooke’s directions, probably represents a young male of this species; but we do not know for certain from what specimen it was taken. The figure of Gray’s _C. melanoprymnus_ in the Zoological Society’s ‘Proceedings’ for 1871 (pl. xliv.) was drawn from a still younger animal, probably of about the same stage as the figure of “_C. punctulatus_” in the ‘Knowsley Menagerie.’ It will be observed how greatly the colour of the back varies in these specimens of different ages. _May, 1895._ [Illustration: THE BOOK OF ANTELOPES, PL. XV. _Smit del. et lith._ _Hanhart imp._ Jentink’s Duiker CEPHALOPHUS JENTINKI. _Published by R. H. Porter._] 20. JENTINK’S DUIKER. CEPHALOPHUS JENTINKI, THOS. [PLATE XV.]