PEOZEUGLODON. 247 



forming the anterior portion of the narrow skull-roof between the temporal fossae, 

 though the sagittal crest is not actually continued on to them. In front of this 

 they widen out suddenly to form the very broad and massive supraorbital processes, 

 which completely overhang the orbits, the skull-roof at this point being very wide 

 and gently convex from side to side. The posterior border of each supraorbital 

 process is concave and its outer end {p.orb., text-fig. 80) is greatly thickened and 

 turned sharply down at right angles to the roof. In front of the orbit also the frontals 

 are thickened and there join a pair of small bones, the lachrymals {la.), which are 

 wedged in between them and the anterior end of the jugal {ju.). In the middle line 

 in front the combined frontals send forwards a wedge-shaped process between the 

 hinder ends of the nasals ; to the side of this they are overlapped, first by the hinder 

 end of the nasals, and external to these by the maxillae, the line of junction running 

 outwards and forwards. The nasals {na.) are of moderate length ; posteriorly, as just 

 mentioned, they are separated for a short distance by the frontals ; in front they meet 

 one another in a median suture. They seem to have been about the same width 

 throughout, but anteriorly they are overlapped to some extent by the facial processes of 

 the premaxillee. Their anterior border in the skull described is incomplete, but it can 

 be seen that they formed the posterior border of the narial opening {nar.), which they 

 overhung to some extent. The rest of the border of the external nares is formed by 

 the large 'premaxillm [pmx.). These are greatly enlarged anteriorly, and are strongly 

 convex on their outer face ; the alveolar border bears the three alveoli of the large 

 incisors, the first being at the extreme end of the snout, while the others are separated 

 from it and from one another by intervals of about 1'5 cm. : on the outer surface 

 behind and above the second and third alveoli are slight depressions for the reception 

 of the points of the lower teeth. Within the alveolar border is a rounded ridge, which 

 is continued back on the maxilla ; there was a short palatine process. The posterior 

 part of the upper surface of the combined premaxillae is gently concave from side 

 to side, and forms the floor of the narial opening, which is not sharply defined in 

 front. Posteriorly the bones send back long facial processes, which are lodged in a 

 groove on the upper anterior borders of the maxillse and form the lateral borders 

 of the narial opening, deepening considerably posteriorly where they join the nasals ; 

 the facial processes extend back to the level of the interval between the second 

 and third premolars. 



The maxillce (mx.) are very large bones : by their upper border they unite with the 

 premaxillae in front, receiving the facial processes of those bones in a deep groove 

 along their upper edge ; behind this they join the nasals. Their posterior edge 

 overlaps the anterior border of the frontals, to the outer side of which they join first 

 the small lachrymals, then the anterior end of the jugals, beneath which, moreover, they 

 send back a short process which bears the alveoli of the posterior molars. There is 

 a large antorbital foramen (ao.f.) opening on to the side of the face at the level of the 



