THE UPPER TRIASSIC OF WESTERN TEXAS. 29 



such as occur in the posterior part of the jaws in the Phytosauria. The sockets of the 

 median part of the series seem a little larger than those of the anterior or posterior ends ; 

 this may be due to the condition of the specimen. Only a single, badly rotted tooth 

 was found associated with the specimen and from this nothing can be made out. 



The nasals are elongate bones lying in the normal position, forming the upper 

 edge of the narial openings and separated from the maxillaries and the lachrymals by 

 distinct sutures. The posterior edge can not be made out exactly, but a suture is 

 traceable for a short distance from a point a little in front of the posterior edge of the 

 antorbital opening toward the median line. 



No trace of a septo-maxillary can be made out. 



The lachrymal forms the upper border of the antorbital opening and is separated 

 from the nasal and the prefrontal by a distinct suture. It forms the broad bar between 

 the orbit and the antorbital opening and joins the maxillary below, but the suture, as 

 stated above, can not be made out definitely. The portions of the lachrymal and the 

 maxillary adjacent to the upper part of the antorbital opening are smooth and evidently 

 afforded attachment to a strong muscle which helped to close the jaws. The upper 

 portion is marked by a deep but relatively small sculpture. A foramen enters the 

 bone on the inner rim of the orbit. 



The jugal occupies the normal position, forming the posterior half of the lower 

 rim and the lower half of the posterior rim of the orbit. The union with the maxillary 

 is sharply defined. The posterior border of the notch beneath the orbit is formed by 

 the jugal. The lower border rises sharply from the posterior lower corner of the notch 

 to the articular region of the skull. The suture between the jugal and the postorbital 

 is very distinct : the two bones meet at about the middle of the slender postorbital bar. 

 The jugal narrows towards the rear and forms the major part of the bar closing the 

 temporal opening below. Neither the position nor the outline of the jugal-quadrato- 

 jugal suture can be made out. 



The limits of the quadratojugal can not be made out, but it is evident that it is 

 a small element. The posterior lower angle of the skull is narrow and the bar behind 

 the temporal opening is even narrower. The whole region is more slender than appears 

 at first sight, for the distal end of the opisthotic appears on the lateral surface and 

 increases t lie apparent size of the angle when seen in profile. 



The sutures outlining the prefrontal, poslfrontal, and frontal can not be followed; 

 the whole region is very rugose and the most careful inspection has failed to reveal more 

 than short traces of the lines of separation. 



The postorbital. — Just posterior to the heavy rugose knob which marks the upper 

 posterior angle of the orbit, a suture can be traced for a short distance upon the smooth 

 surface of the skull on both sides; this evidently marks the posterior edge of the post- 

 orbital. 



The squamosal begins at the suture just mentioned; the anterior part lies in the 

 smooth area above the temporal foramen; the posterior portion is slightly but abruptly 

 elevated and forms a protecting point on the back of the skull. The edge of the abruptly 

 elevated portion is continued downward and backward and forms the posterior edge of 

 the lateral temporal opening until it meets the quadratojugal at some undetermined 

 point. 



The upper surface of the skull (fig. 7 A and plate 5 a). — The skull is narrow in front 

 and gradually widens to the posterior edge. The nasals form a little more than the 

 anterior half; their surface is sculptured a little more deeply on the median than on the 

 outer parts. The median suture is traceable to the posterior edge of the nasals, but 

 from there back is indistinguishable; it is entirely obliterated in the parietal region, 



