CLASSIFICATfON OF THE THKRIODONTIA. 



41 



nearly square in section, the lachrymal region being excavated 

 into shallow hollows overhung by a thickening of the prefrontal, 

 which forms the lateral border of the flat dorsal surface. Further 

 forward the snout becomes deeper, the nearly flat lateral surface 

 passing by a rounded corner into the dorsal surface. There is a 

 long broad swelling on the maxilla over the root of the canine. 



The interorbital and parietal regions are both very broad, the 

 latter passing smoothly into the broad occipital surface. The 

 part of the occiput preserved consists mainly of the very broad 

 interparietal, whose sutures with the tabulars are shown. The 

 supraoceipital has only a very shallow exposure below the inter- 

 parietal. A pecidiar feature of this skull is the irregular shape 

 of the pineal foramen and the fact that- that opening is raised 

 on a little column standing up above the general level of the 

 parietal region. 



Text-fioui/e 5. 



Gorgonops torvwt Owen. Type- specimen. 



Right lateral aspect. X|. Parts in broken lines restored without evidence. 



Ju„ jugal; Lac, lachrymal ; Mx., maxilla; P. Mx., premaxilla. 



The general structure of the dorsal and lateral surfaces will be 

 best understood from text-figs. 4 & 5. The cruciform shape of 

 the pair of frontals is noticeable. 



The structure of the external nostril is very Avell shown in the 

 specimen. The dentigerous part of the premaxilla is deep, and 

 articulates directly with the anterior end of the maxilla, which 

 overlaps on to it. The dorsal surface of the two bones is the 

 lower margin of the nostril and forms the emplacement of the 

 septomaxilla. Behind the nostril the maxilla rises to a long 

 suture with the facial part of the septomaxilla; behind this bone 

 it reaches the nasal. The nasals form a slightly coved roof to the 

 olfactory chamber and reach forward almost to the end of the 

 nose, where they terminate in a nearly straight margin, from the 

 middle of which arises the narrow process which articulates with 



