OSTEOLOGY OF AMERICAN PERMIAN VERTEBRATES 373 



The squamosal is a flat and thin bone which fills out the broad 

 expanse of the sides of the skull back of the jugal. It has a very 

 slender connection with the outer border of the quadrate above, 

 and extends downward very nearly to the cotylar margin. At 

 its upper angle, just back of the hind end of the postorbital, it has 

 a facet for union with the tabulare. Below, the bone forms nearly 

 the whole of the lower margin of the arcade. I can find no evidence 

 of a distinct quadra tojugal; if such a bone was present it is so 

 firmly fused with the squamosal as to be indistinguishable in any 

 one of the four sides in which the squamosal is preserved nearly 

 entire. In front the bone reaches forward to the hind border of 

 the jugal in one case; in others the anterior part is deficient, so 

 that I cannot be quite sure of the relations here of postorbital and 

 squamosal. It is not impossible that my identification of tabulare 

 and squamosal may be contested — there has been such a vast deal 

 of speculation about the temporal arches that one must expect 

 more — and that what I call the tabulare may be declared to be the 

 squamosal and my squamosal the quadratojugal. But, inasmuch 

 as such an interpretation will be speculation purely and impossible 

 of proof, I am not disturbed by the possibility. 



The quadrate is more or less exposed in three cases; in one it 

 is nearly wholly exposed on the front side. It is expanded, some- 

 what fan shaped above, and is thinned. It is visible on the outer 

 side narrowly behind the squamosal attachment. It articulates 

 with the end of the tabulare above, with the paroccipital on the 

 inner side, and with the squamosal on the outer side, as described 

 for that bone. Just above the cotylar margin there is a free, 

 concave surface, bridged over possibly by the lower part of the 

 squamosal. If so, there would seem to be a small quadrate fora- 

 men here, arguing the presence of a quadratojugal bone. But 

 I do not think that the evidence is conclusive. The quadrate 

 stands somewhat obliquely, with the outer, gently curved, and 

 thicker margin forming the posterior border of the temporal region ; 

 its anterior border is directed forward and inward, and is con- 

 tinuous with the posterior process of the pterygoid. Just how 

 much of this part is pterygoid and how much quadrate I cannot 

 say. 



