A NEW PHYTOSAUR FROM THE TRIAS OF ARIZONA 151 



modified palate of the eusuchian crocodiles ? As for the first of these questions 

 I feel that there is no escape from an affirmative answer; an examination of 

 the palate of either Mystriosuchus or Phytosaurus [Lophoprosopus] shows a pair 

 of longitudinal palatine ridges .... which plainly represent the beginnings of 



a secondary palate 



The rounded inner border [of the portion of the palatine about the base of 

 the narial vault] projects very slightly toward the middle line, so that the 

 palatal aspect of the cranium exhibits two elongate ridges which approximate 

 each other within 25 mm. at the level of the anterior border of the nares, 

 diverging gradually behind this region. These palatine ridges partly obscure 

 the outer part of the narial cavities and are continued anteriorly on the maxil- 



laries, but fade out posteriorly without involving the pterygoid It 



should be explained that these ridges do not present a sharp edge, but are 

 broadly rounded. Nevertheless it is an approximation of the palatines, 

 ventral to the internal nares and the pterygoids, and it seems to me that it must 

 be interpreted as a tendency toward the formation of a secondary palate 



In the present form this tendency is so marked that there can 

 be no doubt as to its meaning. The narial vault has its greatest 

 width somewhat back of the nares. The cavity is still partly 

 filled with matrix, but is at least 80-90 mm. wide and somewhat 

 over 50 mm. high. So restricted is the arch at the lower palate 

 plane by the median extension of the palatines, that the opening 

 as seen in a palate view is little more than a slit, not over 24 mm. 

 wide near the posterior border of the nares and gradually widening 

 to the region of the interpterygoid vacuities. This constriction in 

 the narial region is in the form of sharp-edged, thin, horizontal 

 plates extending beneath the narial vault at the plane of the 

 palate. The suggestion of an unfinished or rough edge bespeaks 

 a cartilaginous or fleshy continuation. It is believed that the 

 air passage was thus completely closed below for a considerable 

 distance back of the nares. 



The alveolar ridges cannot be considered as part of this ''false 

 palate," as is suggested by the foregoing quotation. In the present 

 form they are quite distinct from the palatine extensions beneath 

 the nasal vault. These alveolar ridges, always conspicuously 

 developed in the phytosaurs, should probably be looked upon as 

 buffers to prevent the breaking or interlocking of the teeth through 

 the sharp snapping of the jaws in an unsuccessful attempt at seizing 

 prey. 



