I50 MAURICE G. MEHL 



ings are evident in a comparison of Figure 2 with that of M. 

 validus.^ 



THE PALATE 



The palate of this specimen (Fig. 3) seems very little distorted, 

 but although the configuration of the bones is readily determined, 

 some of the sutures are obscure. The bones are thin and over- 

 lapping, and the sHghtest abrasion tends to obliterate the unions. 



The palate is marked by the characteristic phytosaurian ridges 

 just within the alveolar border. These start indistinctly near the 

 third tooth back of the down-turned terminus of the rostrum and 

 increase in prominence to a point a little in advance of the internal 

 nares. From here they flatten out posteriorly and lose their 

 identity before the last tooth is reached. A slight median ridge, 

 low and rounded, continues forward from the internal nares to 

 about mid-length of the rostrum. 



In the region of the twenty-third tooth, there is a conspicuous 

 lateral expansion or swelHng of the rostrum. The alveolar lidges 

 broaden in this region to fill in the increased width. 



Among the most striking features of the palate is the develop- 

 ment of the narial arch. In Angistorhinus ,^ from the slight arching 

 formed by the alveolar ridges far forward, the height increases 

 gradually until it is broad and marked just in front of the nares. 

 Here the height increases rapidly to about 42 mm. at the posterior 

 end of the nares. At this point the arch has a width of 82 mm. 

 In this genus there is not the shghtest suggestion of the con- 

 striction of the arch at the lower palate plane, the suggestion of a 

 primitive false palate. 



In Mystriosuchus, as McGregor has shown,^ the constriction of 

 the narial arch at the lower palate plane is marked. To quote: 



This arched condition of the palate suggests two questions of great impor- 

 tance in their bearing upon the genetic relationships of the group, namely: 

 (i) Do the Phytosauria exhibit the incipient formation of a secondary palate ? 

 and (2) if so, is this the first step in a phyletic series, culminating in the highly 



' Mehl, op. cil., p. 8, Fig. 2. 



^ M. G. Mehl, "The Phytosauria of the Trias," Jour. GeoL, Vol. XXIII (1915), 

 No. 2, pp. 129-65. 



3 McGregor, op. cit., pp. 42-43. 



