372 S. W. WILLISTON 



ever since, though it is only very recently that any other writer 

 has accepted my contention. Three years ago I again expressed 

 my opinion as follows: "I have long believed that the small 

 element intercalated between the paroccipital and the so called 

 squamosal of the lizards corresponds to the epiotics of the stego- 

 cephs,"^ etc. 



In front of the parieto-tabulare arch the side of the parietal is 

 concave and free, forming the upper, inner margin of a typical 

 supratemporal vacuity. It was this free border, seen in two speci- 

 mens, which convinced me originally of the presence of a temporal 

 vacuity in the skull of Araeoscelis. 



The relations of the postfrontals and postorhitals are shown in 

 four specimens. The postfrontal is a small bone which forms the 

 upper, posterior border of the orbit, extending forward on the frontal 

 margin not quite to the middle. Below, near the middle of the 

 postorbital, it unites by a slender squamous underlap with the 

 slender postfrontal process of the jugal. In five different speci- 

 mens this suture is seen, but more positive evidence is furnished 

 by another in which the jugal had been separated a httle distance 

 from the postfrontal, showing the dehcate striated sutural surface 

 for their union. The postorbital unites with both postfrontal 

 and jugal by a convex suture, which approaches near its middle 

 very near the orbital margin. Above, the postorbital reaches 

 narrowly to the parietal, back of the postfrontal. In one speci- 

 men these bones have been separated from the frontal and parietal, 

 leaving the striate sutural surface free. Below, the somewhat 

 thinned anterior part of the postorbital extends downward between 

 the jugal and squamosal at least a third of the way to the lower 

 margin of the arch. Although in one specimen the lower border 

 seems to be complete, I cannot be quite sure of its extent. From 

 this expanded anterior part the bone contracts to extend more and 

 more slenderly very nearly to the tabulare, thus forming nearly 

 the whole of the outer border of the temporal vacuity. Along its 

 whole lower border it is suturally united with the squamosal. 

 These relations are corroborated in so many specimens that there 

 cannot be the shghtest doubt on the subject. 



' Williston, Amer. Jour. Anat. (1910), p. 82. 



