QO AMERICAN PERMIAN VERTEBRATES 



curvature of the upper posterior border of the vacuity cannot be 

 determined. In one specimen the arch is very complete and undis- 

 torted, but it has been partly broken away from the side of the 

 skull above and pressed outward and downward; in the other the 

 outline seems to be quite normal, as I have figured it. The vacuity 

 is very large, comprising nearly the whole of the side of the skull 

 back of the orbits, with thin margins above and on the sides, open 

 for the greater part of the distance below between the teeth and 

 the quadrate. In this space the quadrate is shown in both speci- 

 mens as a broad, oblique plate extending inward and forward, 

 nearly as far as the posterior border of the orbit, articulating above 

 and exteriorly with the suspensorial arch, doubtless chiefly the 

 squamosal; below and within with the pterygoid. Its articular 

 surface below is broad from side to side. The squamosal doubtless 

 reaches nearly to the articular end on the outer side. There are 

 no indications of sutures here, as generally elsewhere. Doubtless 

 also the quadratojugal is entirely wanting. 



The palatal region, as already stated, cannot be laid bare from 

 below, because of the mandibles, but in one specimen the ptery- 

 goid and palatines have been laid bare from above back of the front 

 margin of the orbit. They meet or nearly meet in the middle line 

 below the orbits and seem to be in contact with the descending 

 plates from the f rentals; they are in close contact on the sides 

 with the maxillae as far back as their extremity; back of these is 

 the free transpalatine process, which reaches as far as the extremity 

 of the jugal and a considerable distance back of the orbit. 



The teeth are slender and conical, extending back to the extrem- 

 ity of the maxillae and for some distance back of the orbits and 

 below the temporal vacuity. I count not more than thirty in each 

 maxilla, with not more than three in each premaxilla. Opposite 

 the pronounced antorbital ridge, directed downward and forward 

 from the antorbital elevation and at about two-fifths the distance 

 between the orbit and the hind margin of the nares, there is a stout 

 maxillary tooth on each side, nearly twice the length of those in 

 front and behind. The other maxillary teeth are of nearly equal 

 size, perhaps somewhat smaller in front. The most anterior one 

 of the premaxillae is a little elongated. The mandibles are so 



