MORPHOLOGICAL REVISION 69 



region. Near the upper end the quadrate turns to the rear and joins a process of 

 the paroccipital; the turn in the quadrate is marked by a sharp angle quite similar 

 to that seen in the same position in the turtles. No traces of a columella was found 

 and if present it must have been very short. The opening of the auditory canal 

 can not be made out, but it must have been almost opposite the angle described. 



The outer face of the quadrate is concave, form- 

 ing a funnel-like cavity with the apex at the notch de- 

 scribed above. The whole surface of this concave face 

 is smooth, and anteriorly it is overlapped somewhat by 

 the posterior edge of the squamosal The posterior edge 

 is covered by a bone whose upper limits can not be Fig. 21. — Lateral view of skuii 

 determined, but which is separated from the quadrate 



below by a quadrate foramen of good size. The articular face of the quadrate for 

 the lower jaw is wider than long, convex, and is divided into nearly equal parts 

 by a shallow groove running anteroposteriorly. 



The sutures between the bones are no more distinct than on the superior sur- 

 face, but the slight crushing of the specimen has caused some of the bones to break 

 apart slightly, and this with some slight traces of sutures warrants the following con- 

 clusions as to bones of the side of the skull.* 



The squamosal is continued backward at the upper end in a process which 

 overhangs the quadrate and may contain the tabulare, but there is no suggestion 

 of a division. This portion of the bone bears a striking resemblance to the same 

 region in the turtles. The anterior edge of the squamosal is convex forward and 

 joins the postorbital and prosquamosal. 



The prosquamosal covers the quadrate below and articulates posteriorly with 

 the bone which covers the posterior surface of the quadrate and is separated from it 

 by a foramen; this I consider the quadratojugal. Anteriorly, the prosquamosal 

 articulates with the jugal. It will be seen that this bone occupies the position 

 occupied by the quadratojugal in many reptiles. The reason for considering this 

 bone to be a prosquamosal is given in the discussion of the genus Captorhinus, 

 where the position and form of the bones are shown much more clearly (see p. 94). 



The quadratojugal lies on the back of the skull, covering the posterior surface 

 of the quadrate and separated from it by a large quadrate foramen; its limits can 

 not be made out, as no sutures are traceable on the outer surface of the skull. 

 This interpretation of the temporal region of the skull is radically different from 

 that assumed by Cope. He believed that the Diadectidce had the full complement 

 of bones, such as he figured in Captorhinus (Pariotichus), and upon this basis 

 considered the Cotylosauria as possessing the most primitive type of skull, the 

 one from which all other reptilian types were derived. The impossibility of the 

 Cotylosauria occupying such an ancestral position is apparent, and the equal impos- 

 sibility of any other known form from the Texas Permian occupying such an 

 ancestral position is demonstrated in the discussion of the different groups. 



The jugal forms the lower edge of the orbit; the suture between it and the max- 

 illary is not certain. 



The maxillary probably forms a part of the lower edge of the orbit. It does 

 not reach far up on the side of the facial region. The number of teeth in the upper 

 jaw, maxillary and premaxillary, is given in the following list as accurately as they 



♦In this determination I wa6 aided by Dr. Broom of Victoria College, Cape Colony, and as we reached a perfect agreement on the 

 determinations it is advanced with some confidence. He gives, however, different names to some bones, as quadratojugal for the 

 bone called here prosquamosal. In his recent paper (10a) he gives a figure of sutures differing slightly from the figure here given, 

 fig. 20, A. 



