THE PHYTOSAURIA OF THE TRIAS 14S 



rami have a thickness of 40 mm. The smallest width of the man- 

 dible is 41 mm., at a point about 60 mm. back of the anterior end. 

 From here the width increases gradually to about 90 mm. at the 

 posterior end of the symphysis. The anterior end is considerably 

 enlarged for the reception of the large terminal teeth. The greatest 

 width of this expanded portion is 73 mm. The lateral margins are 

 upturned so as to form a very conspicuous anterior-posteriorly 

 directed groove along the median Hne. This is 31 mm. wide at the 

 top and is broadly excavated to a depth of 9 mm. From the tip 

 of the mandible to the posterior end of the symphysis the length is 

 about 430 mm. The total length \.: about 9' -am. The external 

 naxillary fti^stra is a ^ut 200 mm. ." " -i, / '' mm. wide, with 



rounded anterior anu ^ sterior border... On._, j alveoli remain in 

 the lower jaw upon which to base a description of the teeth. About 

 36 of these are present now on one side. There were probably 10 

 more present in the fragment which is now missing above the 

 anterior end of the external maxillary fenestra, making about 46 

 alveoli in all. Three of these are placed in the expanded upturned 

 anterior portion of the jaw. They are circular in section, as are 

 all the alveoli, and greatly enlarged. The anterior one on each side 

 is 12 mm. in diameter, the next two are of about equal size and 

 measure 16.5 mm. in diameter. If the supposition that the tooth 

 shown in Fig. 8 is one of these anterior teeth of this or a similar 

 species is correct, we may assign a length of some 45 mm. or more 

 to the teeth of the terminal expansion. The two anterior alveoli 

 which are separated by the median channel mentioned above are 

 about 24 mm. apart. Between the first and second and the second 

 and third teeth only a thin film of bone intervenes. Between the 

 last tooth of the terminal, enlarged series and the following one, the 

 fourth, there is a space of about 15 mm. The alveoli back of the 

 three large anterior ones vary considerably in diameter, ranging 

 from 8 mm. to 16 mm. In a general way they increase in size 

 posteriorly, but this is irregular, some of the largest being placed 

 near the middle of the row. In consequence of this irregularity in 

 the size of the alveoli there is an irregularity in the intervening 

 spaces. These spaces range from a thin film to about 8 mm. in 

 width, the greater spaces being, in general, in the anterior portion of 



