The Common Duiker is not unfrequently brought alive to this country, and examples may be seen in most of the European Zoological Gardens. On reference to our Zoological Society’s catalogue it will be found that examples of the Duiker-bok were received in 1867, 1872, and 1876. Since that period the register of the Society shows that as many as eleven examples have been received up to the end of last year. These have been of both sexes, and, according to the testimony of the keepers, most of, if not all, the females have carried short horns. But the Duiker-bok does not thrive in captivity in this country, and most of the specimens acquired have been short-lived. Our two illustrations of the Common Duiker (Plate XXIII.) were prepared by Mr. Smit under the direction of the late Sir Victor Brooke. The lower figure represents the more uniformly-coloured and typical form; the upper shows the variety which has been called _ocularis_ and is known by its more rufous head, whitish eye-stripe, and much paler inferior surface. _August, 1895._ GENUS II. TETRACEROS. Type. _Tetraceros_, =Hardwicke=, Trans. Linn. Soc. xiv. p. 524 (1825) T. QUADRICORNIS. Size small; build slender; anteorbital glands large, oval, opening into a short deep slit on each side of the muzzle; crown not tufted; tail short; mammæ four. Skull with large lacrymal fossæ; upper molar teeth without additional columns. Horns normally four, the posterior, which correspond to the ordinary pair found in _Cephalophus_, placed as in that genus and similar in character, but directed more vertically upwards; anterior pair placed on the front part of the frontals, level with the front of the orbit, much shorter than the posterior pair, and often entirely absent. Female hornless. _Distribution._ Peninsula of India. This genus, the Indian representative of _Cephalophus_, contains only the Four-horned Antelope and its two-horned subspecies. The latter we follow Mr. Blanford, the latest and best authority on the subject, in considering as not specifically separable; but we have some hesitation in doing so, and have treated it as at any rate deserving the position of a recognizable subspecies. Illustration: THE BOOK OF ANTELOPES, PL. XXIV. _Wolf del. Smit lith._ _Hanhart imp._ The Four-horned Antelope. TETRACEROS QUADRICORNIS. _Published by R. H. Porter._] 39. THE FOUR-HORNED ANTELOPE. TETRACEROS QUADRICORNIS (BLAINV.). [PLATE XXIV.] Subspecies T. Q. TYPICUS. _Cerophorus (Cervicapra) quadricornis_, =Blainv=. Bull. Soc. Philom. 1816, pp. 75, 78; =id.= Journ. Phys., Aug. 1818, pl. fig. 3 (skull); _id._ Oken’s Isis, 1819, p. 1095, pl. fig. 3 (skull).