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Show 1873.] SIR V. BROOKE ON THE GENUS GAZELLA. 551 rufous tint than the fawn-colour of the shoulders, upper parts of the back, and haunches. Ears long. Horns in both sexes, but very small in the female; in the male they are truly lyrate, strongly annulated, and massive, of moderate length. Knee-brushes absent. Height at shoulder about 30". Skull: nasal bones rather elongated and pointed. Dentition i.-g, c. -x, p. 2, m . ^; the first premolar in the upper jaw is almost rudimentary, its opposing tooth in the lower jaw is wanting; in the milk-dentition, however, the first of the three lower molars is represented by an exceedingly small cylindrical tooth. Hab. South Africa. This species does not appear to occur in the Zulu country. I now propose to consider briefly whether the theory of evolution offers any reasonable manner of accounting for the present differentiation and distribution of the group. I shall first glance at the chief facts bearing upon this question which are afforded by the differentiation and distribution of the Antelopes in general, both in past and present times. I shall then point to the principal deductions which these facts suggest, and shall conclude m y remarks by laying before the Society an hypothesis which appears to m e to account reasonably for the facts as we now find them. In looking back to our earliest knowledge of the Antelopes, which dates from the later Miocene ages, several important facts present themselves. Foremost amongst these is the great fact that the platform upon which Antelope life was exhibited in the Miocene and Pliocene periods differed certainly in its extent, and possibly in its entire geographical position, from that upon which we now find the form most richly represented. A n examination of the composition of this ancient northern Antelope fauna reveals two striking features :- first, the varied and strong differentiation which had taken place in the form even at this early period; and, secondly, the fact that mixed with many modifications which have entirely disappeared, were found types identical (speaking broadly) with some of the most important generic forms amongst the exististing Antelope fauna. For instance in the Paleeoreas lindermayeri of Wagner we have an animal which may be fairly taken as representing the genera Oreas and Tragelaphus, in the strongly keeled horns more nearly resembling the former, in its smaller size and more delicate build the latter genus, while in the form of skull it closely agrees with both the existing genera. In the extinct form Palceoryx, the existing Oryx finds a representative ; in Antilope paleeindica (Falconer) all the characteristic features of the skull of Alcelaphus are represented, and in Antilope recticornis (Gervais) those at present peculiar to that of Hippotrayus. Nor is the group at present under consideration unrepresented. Differing in structure in only two characters of importance from existing Gazelles, is the Gazella brevicornis oi Gaudry, large quantities of the remains of this species having been found by him at Pikcrmi, |
