318 



MR. G. BLAINE ON THE ZEBRAS 



111 the following table the difl'erences between the skulls of 

 Hippotragus luger and Hipjyotragus variani are set forth : — 



H. niger. 



Pace shorter and broader, the frontal 

 tield which gives rise to the horns 

 being more prominently developed, 

 with the bases of tlie horns directed 

 more obliquely backwards. 



Nasals shorter, their frontal extremities 

 not reaching the plane of the ante- 

 orbital processes. 



Premaxillse less spatulate. 



Lacrymal depression scarcely defined. 



Orbits round. 



Maxillse showing a distinct groove 



running parallel to the inferior border 



of the nasals, and continued across the 



iipper ends of the premaxillaj. 

 Tympanic bulla3 small, with styliform 



process flattened and blade-like. 



Paroccipital processes wide,flattened,with 

 posterior margins convex. Viewed 

 from behind they curve slightly out- 

 wards, then downwards and inwards 

 at their apices, a large portion of their 

 posterior borders being on a level with 

 the posterior face of the condj'les. 



Foramen ovale large and oval. 



Mesopterygoid fossa wide, triangular in 

 shape, with its containing walls 

 diverging from the basisphenoid down- 

 wards, the post-hamular margins 

 forming everted flanges. 



Lateral fossae wide. 



H. variani. 



Face longer and narrower, with less ex- 

 tensive frontal field and the bases of 

 the horns rising nearly vertically and 

 directly over the orbits. 



Nasals longer, their frontal extremities 



reaching the plane of the ante-orbital 



processes. 

 Premaxillse spatulate, with broadly 



flanged anterior margins. 

 Lacrymal depression clearly defined. 

 Orbits oval, the vertical axis being longest. 

 Maxillce showing only faint traces of 



groove. 



Tympanic bullas large, with styliform 

 process round, very small and spike- 

 like. 



Paroccipital i^rocesses narrow, with 

 straight posterior margins and no 

 lateral curvature, but having a strong 

 forward and slight inward inclination. 

 They are more forward in position, 

 being almost wholly in advance of the 

 condyles. 



Foramen ovale small and round. 



Mesopterj'goid fossa narrow, with 

 parallel walls. 



Ascending wall of maxilla behind tlie 



tooth-row nearly vertical, and strongly 



carinated. 

 Posterior palatine notches in line with, 



or in front of the plane of the posterior 



edges of the last molars. 

 Teeth smaller. 



Lateral fossae narrower, being constricted 

 by the inflation of the posterior ascend- 

 ing walls of the maxilla?. 



Ascending wall of maxilla behind the 

 tooth-row obliqueb' directed with its 

 suface inflated, and less carinated. 



Posterior x>alatine notches behind the 

 plane of the posterior edges of the 

 last molars. 



Teeth larger. 



The skull of H. equinus resembles that of H. niger, and differs 

 from H. variani in the form and position of its paroccipital pro- 

 cesses, in the open ti-iangular outline of the mesopterygoid fossa, 

 and in the vertical direction of the ascending walls of the maxillae, 

 which are laterally compressed and prominently carinated. 



