_Cephalophus rufilatus_, =Gray=, Ann. Mag. N. H. (1) xviii. p. 166 (1846); =id.= List Ost. Sp. B. M. p. 56 (1847); =id.= Knowsl. Men. p. 10, pls. vi. & ix. (animal) (1850); =id.= P. Z. S. 1850, p. 123; =Turner=, P. Z. S. 1850, p. 170; =Gray=, Cat. Ung. B. M. p. 85 (1852); =Temm.= Esq. Zool. Guin. pp. 194, 221 (1853); =Gerr.= Cat. Bones Mamm. B. M. p. 236 (1862); =Fitz.= SB. Wien, lix. pt. 1, p. 166 (1869); =Gray=, P. Z. S. 1871, p. 597, fig. 5 (skull); =id.= Cat. Rum. B. M. p. 26 (1872); =id.= Hand-l. Rum. B. M. p. 95 (1873); =Scl.= List An. Z. S. (8) p. 147 (1883); =Jent.= Cat. Ost. Leyd. Mus. (Mus. Pays-Bas, ix.) p. 132 (1887); =id.= Cat. Mamm. Leyd. Mus. (_op. cit._ xi.) p. 162 (1892); =Thos.= P. Z. S. 1892, p. 423; =Matsch.= MT. deutsch. Schutz-geb. p. 81 (1893); =Lyd.= Horns and Hoofs, p. 211 (1893). _Antilope (Cephalolophus) rufilatus_, =Wagn.= Schr. Säug. Supp. v. p. 425 (1855). _Cephalophus rufilatus cuvieri_, =Fitz.= SB. Wien, lix. pt. 1, p. 166 (1869). VERNACULAR NAME:--_Coquetoon_ on the Gambia (_Whitfield_). Size small; form slender. General colour partly bright yellowish rufous, and partly a peculiar bluish grey; the former colour covering the sides of the face, the whole of the neck, the shoulders, flanks, rump, and belly, while the latter prevails on the middle line of the nose, on the forehead, occiput, back of ears, centre of back from withers to rump, and all four limbs, from the elbows and middles of lower legs downwards. Crest long, blackish. Tail rufous above basally, black terminally. Horns placed in the same line as the nasal profile; those of male short, conical, pointed (but no adult wild specimen is available for description); those of female rudimentary, mere low rounded knobs, hardly projecting above the skin of the head. Skull with a long and slender muzzle. Anteorbital fossæ remarkably deep, more so than in any other species. Mesial palatal notch about a quarter of an inch anterior to the lateral ones. Dimensions:--♂. Height at withers 14 inches, ear 2·3, hind foot 7. Skull (♀): basal length 5·2, greatest breadth 2·6, orbit to muzzle 2·9. It is difficult to say to which of the other species this peculiar little animal is most nearly allied, especially in the absence of wild-killed male specimens with fully developed horns. _Hab._ West Africa, from Gambia to the Niger. The ninth and last species of the group of Bay Duikers, though agreeing with the preceding species in its generally rufous coat, is distinguishable by its smaller size and lighter colour. The front and dorsal stripe are of a peculiar bluish grey instead of being black, and the whole of the flanks and sides are of a light yellowish rufous.