AESINOITHERITIM. / 



from the parietals and sharply defines the upper border of the temporal fossa. It 

 ends some distance in front of the small horns, and its termination may be taken 

 as marking the posterior limit of the upper border of the orbit, there being no 

 definite postorbital process. The antero-superior portion of the orbital border is 

 formed by the frontal ; it is broadly rounded, and at one point near the middle it is 

 crossed by a broad shallow depression, which runs upwards and forwards on to the 

 side of the base of the horn, where it divides into three or four divergent branches, 

 forming deep channels in the bone (PL I., b.v.). These channels evidently lodged 

 blood-vessels which served for the conveyance of blood to or from the covering of the 

 horn, and judging from the marked way in which both these vessels and those on 

 the anterior face of the horns impress the bone, it seems probable that the covering 

 was hard and of much, the same nature as that clothing the horn-cores of the 

 cavicorn ruminants. 



The lachrymal {I.) is a small bone occupying the anterior angle of the orbit, 

 wedged in between the frontal above, and the maxilla and jugal below. It bears 

 a vertically-elongated prominence (see PI. I., I.) which forms the actual edge of 

 the orbit and is connected below with a strong crest borne on the front of the 

 maxillary process of the jugal. There seems to be no trace of any lachrymal foramen. 



The nasals {na.) are the most remarkable bones of the skull, and they are enormously 

 enlarged, forming almost the whole of the great anterior horns. The sutures between 

 these bones and the frontals have already been referred to : they are open only in the 

 young (PI. III. figs. 2,2 a); in the adult or even three-parts-grown animal they are 

 completely obliterated (PL I. and PL III. figs. 1, 1 a), and the same is the case with, 

 the suture between the nasals themselves. On the side of the face the ventral border 

 of these bones unites first with the upper edge of the maxilla, and in front of this 

 with the premaxilla, the suture with which is continued forwards just into the nasal 

 cavity. Here a downgrowth of the lower surface of the portion of the nasals forming 

 the roof of the nasal cavity unites with a corresponding upgrowth of the maxilla 

 which overlaps it (text-fig. 2). The two form a sort of column on either side of the 

 posterior face of the nasal cavity, and these columns help to support and form a 

 base for the horns. Furthermore, owing to their presence the nasal passage is greatly 

 contracted and forms a vertical cleft between them. The roof of the nasal cavity is 

 nearly flat and in the adult its edges are thin, sharp, and somewhat everted (PL I., 

 PL II. fig. 1a): in the young, on the other hand, this edge is wanting (PL III. 

 figs. 2 A, 2 b), so that the nasal roof passes by a gentle curve into the outer face 

 of the horn. In the young also the anterior ends of the nasals are free and not 

 connected by a bar of bone with the premaxillse. This bar, which is formed only 

 at a comparatively advanced age, appears to result from the ossification of the 

 anterior edge of a cartilaginous nasal septum, the presence of which is indicated 

 by the peculiar groove (PL III. figs. 1 A, 2 b, ms.g. ; see also text-fig. 2, mes.g) 



