Stniciure of the Therocephalian Skull. 



G9 



parietal and preparietal and laterally with the postfrontal ; 

 tliey form at any rate a small part of the upper rim of the 

 orbit. 



The postorbital is a large bone forming the whole of the 

 back of tlie orbit and articulating below witli the jugnl. It 

 has a long procss running back in contact with the parietal 

 to the squamosal. The outer edge of this bone forms the 

 whole of the anterior and superior borders of the temporal 

 fossa. 



The postfrontal is a rather large triangular bone lying 

 between the frontal, parietal, and postorbital, and forming a 

 good deal of the border of the orbit. It is entirely excluded 

 from the temporal fossa. 



Eth. 



Frk.Sph. 



Same skull as the preceding figures. Anterior view of the broken front 

 face of the specimen. 



Reference-letters as before, with : — Eth., ethmoid ; 

 Pab.Sph., parasphenoid. 



The baslsphenoid and parasphenoid are indistinguishably 

 fused. They articulate behind with the basioccipital and 

 send out a process which forms the outer wall of the pit 

 which encloses the fenestra ovale. In front of this region 

 the conjoint bone narrows very rapidly ; the nearly vertical 

 sides bear very curious basipterygoid processes, which are 

 entirely laterally directed and apparently quite thin. The 

 very narrow anterior prolongation of the bone wiiich separates 

 the pterygoids for a long distance is presumably entirely 

 parasphenoid. There are no carotid foramina. 



