200 



TEETIAEY VEETEBEATA OP THE EAYTJM. 



Eather in advance of its middle point, and about beneath the anterior border of the orbit, 

 its front portion is bent down, making an angle of about 140° with the posterior part. 

 The alveolar border forms a double curve ; posteriorly it is convex outwards, so that 

 the palate is much wider opposite the middle molars than at any other point. In the 

 premolar region the border is concave outwards, so that the palatal surface is greatly 

 narrowed, the narrowest point being about opposite the tooth here called the second 

 premolar. In front of this the border thickens and turns outwards to the canine 

 alveolus (c), immediately in front of which is the maxillo-premaxillary suture. On the 

 palate the maxilla extends rather further forwards, terminating as the posterior edge of 



Text-fig. 64. 



Middle portion of roof of skull of Eosiren lihyca. 

 fr., frontals ; ma., nasals ; pa., parietals ; pma;., premaxilliB. | nat. size. 



the large median anterior palatine foramen {a.p.f.). The facial surface of the anterior 

 part of the maxilla is nearly flat and vertical. Posteriorly it bears a broad shelf-like 

 zygomatic prominence, which forms the floor of the orbit and is perforated in front 

 by a large antorbital foramen. 



The premaxillm (pmw.) form the greater part of the downwardly turned rostrum ; 

 the suture between these bones and the maxillae, after crossing the alveolar border, 

 runs first upwards and backwards, then nearly directly backwards, terminating about the 

 level of the hinder border of the narial opening {nar.). Here they join the anterior end 

 of the frontals, thus, as above mentioned, excluding the maxillse from any share in the 



