A NEW PHYTOSAUR FROM THE TRIAS OF ARIZONA 153 



the union of the premaxillae and the vomer at the inner posterior 

 border of the nares may be a fracture. If so it is remarkable for its 

 symmetry in relation to the median line of the skull. Of the 

 posterior boundary there can be Httle doubt. It joins the ptery- 

 goid in a forward convex line about 32 mm. back of the internal 

 nares. 



The palatines apparently form a goodly portion of the lateral 

 borders of the internal nares. Aside from this, however, they 

 seem to be largely confined to the lower palate plane. It is thought 

 that their union with the pterygoids and vomers is at or near the 

 base of the narial vault, but of this one cannot be sure because of the 

 matrix-filling part of the cavity. Posteriorly the palatines come 

 to an acute angle, the point of which prevents the articulation of 

 the pterygoids with the ectopterygoids on the palate surface. 



The ectopterygoids are small, triangular bones. The posterior 

 borders are down-curled so as to be conspicuous in a lateral view 

 of the skull. 



The pterygoids are exceptionally large, but are almost entirely 

 confined to the sides and roof of the narial arch. Their extent 

 along the pterygo-quadrate bar cannot be determined. 



The parasphenoid has been destroyed, but it must have been 

 very similar to that shown in the palate restoration. The union 

 between the hasi-sphenoid and the pterygoids and hasi-occipital 

 is as indicated in the restoration. The relation of the other bones 

 of the posterior part of the skull as seen in the palate view cannot 

 be determined. The relations shown are those determined from 

 the University of Wisconsin specimen mentioned above. 



THE TEETH 



With the exception of a few roots and one partially erupted 

 tooth in the middle of the series that shows the crown, all the 

 teeth have been lost. The alveolar margin of the jaw is splendidly 

 preserved for the most part and gives a good indication of the 

 number of the teeth and of their variations in size. 



The alveolae are all distinct and usually separated by a space 

 of at least 3 to 5 mm. In each maxilla there are apparently twenty- 

 four teeth and twenty-three in each maxilla, a total of ninety-four 



