Height at withers about 38 inches. Colour of head, neck, and body in winter a tolerably uniform brownish grey; in summer the hairy covering of the body between the neck and hind-quarters assumes a richer and redder hue, the head and neck remaining the same throughout the year. Mane on forehead nearly black, and back of head behind horns darkish brown; lips and chin white; a broad white stripe on each side of the face extending from near the middle of the cheek upwards in front of and above the eye, and usually meeting its fellow of the opposite side across the upper portion of the nose, though sometimes the union is interrupted in the middle by the black hairs of the frontal mane. Ears mostly white, sometimes blackish at the base; an ill-defined whitish patch sometimes present behind the eye and a black patch on the lower edge of the cheek close to the neck. Fore legs white, with the exception of a brown patch on the knee, a brown rim round the false hoofs, and a tinge of brown which extends downwards on to their upper portions from the shoulder; a black patch sometimes present between the shoulder and the throat; the dark colour of the back and flanks spreads for a short distance on to the hind-quarters; otherwise the hind-quarters, tail, and hind legs are white, the rump and thighs being a dirtier white than the legs. As in the case of the front legs, however, there is a rim of brown hairs round the false hoofs, and the tail-tuft, when present, is brownish. Belly white. Hairs along middle of neck sometimes reversed. The horns attain a length of about 28 inches in a straight line and about 36 following the spiral. Skull and horns as described above. The measurements of a skull are:—Basal length 12 inches, greatest breadth 5·30, muzzle to orbit 8·25. _Female._ Like the male, but horns thinner. _Hab._ Desert-regions of North Africa from Dongola to Senegal. The Addax belongs to the same group of desert-haunting Antelopes as the species of _Oryx_ of which we have just treated, and is essentially of the same structure. But it is at once distinguishable by its spiral horns and expanded hoofs, and may properly be referred to another genus, which Rafinesque in 1815 seems to have been the first to call “_Addax_” adopting the name from Pliny and other early writers. In 1816 De Blainville gave the first scientific description of this Antelope, calling it _Antilope naso-maculatus_, from the conspicuous white blaze across the nose. Combining this with the generic term above mentioned, we obtain “_Addax naso-maculatus_” as the correct scientific name of this Antelope.