The most striking difference between the two species consists in the development of the hairs on the tips of the ears in _O. callotis_ so as to form a long black tuft; in _O. beisa_ the hairs at the extremity of the ear are scarcely longer than those covering the adjacent edges of that organ. Lastly, in _O. callotis_, the hairs along the median dorsal line are reversed in direction of growth from a point, only a little behind the middle of the back; whereas in _O. beisa_ the parting is situated on the rump. _Hab._ British East Africa, south of the River Tana, and interior of German East Africa. Southwards of the River Tana in British East Africa, or thereabouts, the Beisa appears to be replaced by a nearly allied form, distinguishable by the conspicuous tufts which adorn the tips of its ears and by other less noticeable characters. It will be easily understood that this animal was not at once distinguished from the typical form by those who first met with it, and was consequently referred to “_Oryx beisa_” by Mr. Hunter in his Appendix to Willoughby’s ‘Big Game in East Africa,’ and by other earlier authorities. It was not, in fact, until 1892 that the conspicuous difference of this species from _O. beisa_, as regards its ears, attracted notice, when Mr. Rowland Ward, F.Z.S., first called Thomas’s attention to it. Thomas, after examining into the subject, brought it before the notice of the Zoological Society of London on March 15th of that year, and proposed to call the new form _Oryx callotis_. Thomas’s communication was subsequently printed in the Society’s ‘Proceedings’ accompanied by a good coloured figure of the mounted head of the typical specimen, which was subsequently presented by Messrs. Rowland Ward and Co. to the British Museum. As will be seen by reference to Mr. Rowland Ward’s ‘Records of Big Game,’ the horns of this typical specimen are among the shortest of the series of 18 specimens of this species of which measurements are there given, the longest pairs being over 30 inches in length. These latter are, no doubt, those of females, which in all the species of _Oryx_ seem to be rather longer and thinner than those of males. In the first volume of ‘Big Game Shooting’ in the ‘Badminton Library,’ Mr. F. J. Jackson gives us the following account of _Oryx callotis_ in British East Africa:— “The East African Oryx is known to the Swahilis as ‘Cheroa.’ The Cheroa is found in the Kilimanjaro district in greater numbers (particularly near Useri) than elsewhere. It is also plentiful in the Galla country, between the Sabaki and Tana rivers, and I have myself seen it within a mile of the sea at Merereni.