416 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
jugal, or with both to form a broad arcade which bounds the large 
supratemporal vacuity below. 
From the relations of this bone in these three orders to quadrate, 
otic capsule, and the postorbital (or the jugal by a recession of the 
postorbital) it must be regarded as the squamosal. Hence it follows, 
that the upper or more medial element, the supratemporal of the 
Cotylosaurs (as well as the quadratojugal) is unrepresented unless 
fused with the squamosal. In Cynognathus (fig. T) there is in the 
published figures an infratemporal fossa (its existence is denied by 
Broom) and the position of this when compared with Procolophon 
further strengthens the conclusion that it is the true squamosal which 
Fig. T. — Lateral view of the skull of Cynognathus, after Woodward. J., jugal; 
Mx., maxillary; Sq., squamosal. 
persists in these orders. Evidently this was Cope’s (’ 92 ) conclusion 
although he calls that element the supratemporal. 
Broom (: 01 , p. 182) and Williston (: 04 ) state that these orders 
possess the most medial only of the bones of the temporal region of 
the Cotylosaur skull and that the two other elements have disappeared. 
It is evident that they correctly homologized the bone in question with 
the mammalian squamosal but since in other reptiles they gave the 
name squamosal to the medial element of the three, they found it 
necessary to assume that their prosquamosal (squamosal proper) 
and the quadrato jugal had disappeared, which involves the difficulty 
of making the upper element (my supratemporal) assume the primitive 
relations of the elements which have been lost. Baur (’ 94 ) supposes 
(and in this he is followed by Woodward, ’ 98 , and Osborn, : 03 ) 
that the squamosal is really a complex of squamosal and supratemporal 
(prosquamosal), but this conclusion is wholly hypothetical and has no 
evidence to support it. 
