236 Prof. Owen on the Reptilian Fossils of South Africa. 



midspace ; the surface is narrowest behind this foramen, where it is slightly 

 concave and measures but 2 inches 3 lines across : in front of the foramen the 

 cranial roof gradually expands with a flatter surface to the post-frontals (12). 



On each side of the parietal part of the skull the temporal ridges (12, 7) bound 

 a smooth elongated longitudinal concavity for the upper origin of the temporal 

 muscles. 



The frontal region continues increasing in breadth as it advances, and sends 

 outwards an angular, rather rough, obtuse, antorbital process [u], probably formed 

 by the prefrontal. Anterior to this the broad fiat platform of bone begins gradually 

 to bend downwards between the nostrils, PI. XXX., n ; but still expands and over- 

 arches those cavities by a strong tuberosity. Here the breadth of the facial part 

 of the skull is at least 8 inches. 



Judging by the curvature of the upper jaw anterior to the nostrils, and by the 

 portion of the trenchant alveolar border which remains in front of the alveolus of 

 the tusk (21), the anterior contour of the skull must have been such as is indicated 

 by the dotted line at 22, PI. XXX. In this side-view the total length of the skull 

 from the back part of the mastoid root of the zygoma (s) to the end of the jaw so 

 indicated gives 20 inches : the posterior border of the orbit (12, 25) divides this 

 extent into two equal parts, the orbit being in the anterior half, and the posterior 

 half being occupied chiefly by the temporal fossae. 



The posterior boundary of the orbit arches, from above, outwards, down- 

 wards, and backwards, of nearly the same breadth, which is 1 inch 3 lines ; 

 it is composed of the post-frontal (12) and malar (26) bones ; the former descend- 

 ing to the lower border of the orbit, and the latter ascending behind the post- 

 frontal, and gradually terminating in a point about an inch and a half from 

 the upper surface of the cranium : the two bones are thus joined together by a 

 long oblique suture. The malar appears to be continued backwards about three 

 inches, along the inner side of the zygomatic platform, which is formed chiefly by 

 the squamosal. In a second specimen of the skull of the Dicynodon tigriceps the 

 post-orbital boundary descends more vertically, and the orbit is smaller. 



In the more perfect example of the skull, PL XXIX., the orbit on both sides 

 presents a subelongate triangular contour, with the angles rounded off", and the 

 long diameter horizontal : this diameter is 4 inches ; the vertical diameter at the 

 fore part of the orbit is two inches and a half, whence it contracts to the posterior 

 angle. The lacrymal foramen is situated just within the verge of the cavity, at 

 the anterior inferior angle : about an inch above it, projects the antorbital process, 

 divided by a notch and fossa from the supernarial tuberosity. The malar forms 

 the chief part of the lower border of the orbit : it seems to extend to the lacrymal 

 bone, and it rests in that extent upon the maxillary, PI. XXX. (21), which is 



