THE PHYTOSAURIA OF THE TRIAS 



137 



aging about 1 1 mm. in diameter. The third tooth of the premaxillae 

 series crowds close upon the down-curve portion of the rostrum. 

 Back of this they are quite regularly spaced, averaging about 8 mm, 

 between adjacent alveoli, A break across the rostrum near the 

 maxilla-premaxilla union exposed an unerupted tooth very similar 

 to that shown in Fig. 9. 



The maxillae have their greatest extent along the lateral margins 

 of the skull, where they reach a length of about 340 mm. They 

 connect with the jugals near the middle of the antorbital vacuities 

 and form the lower anterior borders of these openings. Above they 



Fig. 5. — Angistorhinus grandis, posterior view of skull, two-sevenths natural size 



connect slightly with the long anterior projections of the lachrymals 

 and more broadly with the nasals. They contain about 19 alveoli 

 each, of about the same diameter as those of the premaxillae. 

 The spacing is much the same with the exception that in the pos- 

 terior ones there is a slight diminution of the interalveolar space. 

 Although little can be said with certainty concerning the crowns of 

 the premaxilla-maxilla teeth, they probably ranged from those with 

 nearly round sections, in the anterior part of the rostrum, to those 

 that are laterally compressed with sharp, serrate anterior and pos- 

 terior cutting edges, A great many of these sorts are found asso- 

 ciated with the phytosaur remains and some of the laterally com- 

 pressed ones were found in a fragment of a skull that very closely 

 resembles the form here described. These teeth will be more fully 

 discussed farther on. 



