THE UPPER TRIASSIC OF WESTERN TEXAS. 51 



The quadratojugal is high behind, forms the posterior edge of the lateral face of 

 the skull, and conceals the quadrate. Its upper anterior edge forms the posterior half 

 of the lower edge of the lateral temporal opening. Its lower edge forms the extreme 

 posterior part of the lower edge of the skull, but is soon covered by the jugal; the suture 

 between these two bones passes obliquely upward and forward. 



The jugal forms the lower edge of the skull as far forward as the anterior end of the 

 lateral temporal opening; it is then covered by the maxillary and the suture between 

 them runs forward and upward, terminating, apparently, on the lower edge of the antor- 

 bital opening, about one-third of the length of the edge from the posterior end. The 

 jugal is deeply notched posteriorly by the anterior end of the lateral temporal opening 

 and forms both the upper and lower edges of this part of the opening. The suture 

 between the jugal and the postorbital lies at the posterior end of the orbit and the jugal 

 forms much of the outer orbital rim. The suture between the jugal and the lachrymal 

 can not be made out. 



The lachrymal can not be delimited with certainty; it probably occupies the same 

 position as in most of the Phytosauria and forms the posterior border of the antorbital 

 opening. 



The maxillary starts from a point below the anterior edge of the lateral temporal 

 opening and forms the lower edge of the skull as far forward as about 3 centimeters in 

 front of the narial opening. Its upper edge forms the anterior two-thirds of the lower 

 border of the antorbital opening. A thin groove, which apparently marks the position 

 of a suture, rises from the middle of the upper border of the antorbital opening and runs 

 forward close to the edge; it is traceable out upon the face of the skull for some distance; 

 it apparently joins the suture between the maxillary and the premaxillary. It is believed 

 that this groove marks the position of the suture between the maxillary and the nasal, 

 as the form of the maxillary thus outlined is found in several genera of the Phytosaurs. 



The nasals can not be exactly outlined. If the suture described above is correctly 

 determined, the nasals form most of the sides of the skull above the antorbital opening, 

 form a part of its upper border, and join the lachrymals and prefrontals posteriorly. 

 Anteriorly the nasals probably form the borders of the narial opening, except, possibly, 

 the median portion of the anterior edge, and send slender processes forward between 

 the maxillaries and the premaxillaries. The septum in the narial opening is in all proba- 

 bility formed by the nasals. 



The premaxillaries. The outline of the posterior end of the premaxillaries is uncer- 

 tain, but they apparently send long processes backward and upward which terminate in 

 the anterior median portion of the edge of the narial opening and join the nasals and 

 maxillaries. Anteriorly they form the major portion of the long, slender rostrum. The 

 anterior end is but slightly decurved, and there is a very shallow constriction just 

 posterior to it. 



The lower surface of the skull (plate 11, fig. c). The bones of the palatal surface 

 have been largely preserved, but have been badly broken, slightly displaced to the left 

 side, and crushed against the lower surface of the bones of the roof of the skull. 



The basioccipital. The condyle is nearly hemispherical and has a rather long neck, 

 with the sides flattened. Low ridges appear near the posterior end of the lower face 

 and rise rapidly forward until just anterior to the suture between the basioccipital and 

 the basisphenoid they form high processes on the sides of a deep notch. 



The basisphenoiil is separated from the basioccipital by a distinct suture. On 

 either side of the notch described above there are prominent processes, the tubera basioc- 

 ci/tilalia, rounded externally and with flat, oval faces looking posteriorly. These pro- 

 cesses contract anteriorly, disappearing just posterior to the origin of the basipterygoid 

 processes. The lower face of the bone is flat and there is no deep pit; the bone is broken 



