208 MR. O.THOMAS ON SOME [Mar. 17, 



appeared that a Reed-buck would occur in the dry sandy plateau of 

 Somali-land. Now, however, that better material is available, I am 

 able to draw up a fairly complete account of the more essential 

 characters of this most beautiful Gazelle, of the discovery of which 

 Mr. Clarke, both as sportsman and naturalist, has so much reason 

 to be proud. 



Muzzle, character of face-markings, and presence of anteorbital 

 glands as in Gazella. General form (as described by Mr. Clarke, 

 see below) and skull more as in Lithocranius. Horns in curve and 

 general appearance as in Cervicapra. 



Coloration of face, using Sir Victor Brooke's phraseology ', as 

 follows : — Central facial band deep rich chestnut-rufous, becoming 

 duller towards the bases of the horns ; light facial streaks pure white, 

 very prominent and sharply defined, extending the whole length of 

 the head from the bases of the ears to the corners of the nostrils, 

 somewhat duller and more indistinct at their extremities, but broad- 

 ening in the middle to encircle the eyes ; dark facial streak present 

 but not strongly marked. Cheeks and sides of neck pale fawn ; 

 throat white. Crown between and behind horns brown or grizzled 

 fawn, the latter condition occurring in the older of Mr. Swayne's two 

 head-skins ; a marked whorl of hairs situated between the ears. Back 

 of ears short-haired, dark fawn hasally, gradually darkening to black 

 terminally ; insides white-haired, but with black tips. 



Horns evenly curved upwards and forwards, the basal halves 

 running backwards and the terminal halves nearly vertically upwards, 

 the m.ain curvature being therefore exactly in the opposite direction 

 to that found in Gazella and Lithocranius. The horns themselves 

 slender, their smooth unridged portion very long, the first indistinct 

 ridge occurring about 5 inches from the tip. Ridges widely separate, 

 strongly defined anteriorly, but becoming abruptly obsolete about 

 halfway round, the sides and back showing scarcely a trace of them ; 

 their number amounting to 10 in the oldest specimen available, a 

 number probably but seldom much exceeded, judging by b and c, 

 which, although fully adult, have only 8 and 7 ridges respectively. 

 Of Mr. Swayne's two specimens one has 8 and the ether 5 ridges. 



Skull diverging from that of Gazella and approaching that of Litho- 

 cranius by being unusually low, long in the occipital region, with a 

 comparatively straight cranio-facial angle, with very small bullae, with 

 the postero-internal wall of the suborbital fossae imperfect, and with 

 a remarkably small and slender lower jaw. On the other hand, it 

 differs from the same skull by being peculiar to a less extent in all 

 these points, by the greater development of the premaxillae pos- 

 teriorly, where they have a broad articulation with the nasals, by 

 the larger nasals and smaller interparietal, and by the larger and 

 more powerful teeth, which are absolutely larger in the smaller 

 animal. 



In its skull-characters, therefore, Ammodorcas stands just inter- 

 mediate between Gazella and Lithocranius ; in its muzzle and in the 



1 P. Z. S. 1873, p. 536. 



