It should be stated that the description given by Pliny of his “_Strepsiceros, quem Addacem Africa appellat_” is very short and incomplete, and has been variously interpreted by subsequent writers. But as it was an African animal with twisted horns, and the native Arab name of the present species, according to Hemprich and Ehrenberg, is “_Abu Akass_” (the father of the twist), it seems highly probable that we have in it the veritable “_Addax_” of the ancients. The first naturalist of modern days to obtain specimens of the Addax in its native wilds was Rüppell, who met with it in the deserts of Dongola south of Ambukol, where, he tells us, it lives in small families apart from all other species of Antelopes, and is hunted by the Arabs on horseback in summer time. Rüppell forwarded examples of both sexes of the Addax to Frankfort, where it was described and figured by Cretzschmar in 1826 from Rüppell’s specimens. Cretzschmar identified it as being without doubt the “_Addax_” of Pliny, and named it _Antilope addax_, being apparently unaware that it had been previously described by De Blainville from specimens which he had examined in London in the Pantherion of Bullock and in the Museum of the Royal College of Surgeons. About the same period Hemprich and Ehrenberg had obtained examples of the same Antelope for the Berlin Museum, apparently from nearly the same district. These were first described and figured by Lichtenstein in his ‘Darstellung der Säugethiere,’ and subsequently by Hemprich and Ehrenberg themselves in their ‘Symbolæ Physicæ.’ They tell us that they were obtained about twenty hours’ distant from Ambukol, in the Chor-el-Lebben, where these animals are hunted by the Kubabish Arabs on horseback, in the month of June. Three specimens were sent home, which we suppose are the same that are figured in their plate, and represent, according to their descriptions, an adult female and two young females with straight horns. Our third great authority on the Mammals of North-east Africa, Th. v. Heuglin, informs us that the Addax extends northwards into the Libyan Desert of Egypt, to the Fayoum and the Oases, and is not rare in the Bayuda Desert. Though he writes as having met with this species himself, he does not give us the exact locality in which he came across it. Passing westwards, we have no doubt of the occurrence of the Addax in suitable localities all through the Great Sahara, although we have little certain information on the subject, except that a pair of horns, brought back by Denham and Clapperton from their adventurous journey across Central Africa in 1822–24, is in the British Museum.