The Red-flanked Duiker, as we propose to call it, appears to have been confounded by Desmarest, Lesson, Gervais, and other French systematists with the _Antilope grimmia_ of Pallas, which is _C. coronatus_--both they and the latter ignoring the fact that the name “_grimmia_” properly belongs to the Common Duiker, _C. grimmi_, of the Cape. This confusion was first properly cleared up by Dr. Gray, as early as 1846, but it is only quite recently that the correct names for the three species have come into general use. Desmarest, in his article on “_Antilope_” published in 1816 in the ‘Nouveau Dictionnaire d’Histoire Naturelle,’ was the first describer of the present animal under the name of _Antilope grimmia_; and in 1821 F. Cuvier, in his ‘Histoire Naturelle des Mammifères,’ gave a figure of it, from a specimen from Senegal, then living in the Jardin des Plantes, under the name of ‘Le Grimm.’ In 1846, in an article published in the ‘Annals and Magazine of Natural History,’ the late Dr. Gray first distinguished the present species from the “Grimm,” and proposed to call it by the appropriate name _Cephalophus rufilatus_. Dr. Gray based his description upon a pair in the Derby Museum, and on a young female in the British Museum which had been presented to that collection by Lord Derby. This last specimen, which may now be seen mounted in the Mammal-Gallery of the National Collection, was obtained on the Gambia by Lord Derby’s collector, Whitfield. The two types in the Derby Museum are stated to have been obtained at Sierra Leone. [Illustration: Fig. 19. Skull of _Cephalophus rufilatus_, jr. (P. Z. S. 1871, p. 597.)]