IN THE REPTILIA. 



19 



orbital would be probable. The arch is then supratemporal, and this element may 

 be fused with the supramastoid in the Dinosauria. 



If the Rhtnchocephalia of the Mesozoic had the same structure as Spheno- 

 don, we may ascribe to them an infratemporal foramen and a zygomatic arch. The 

 former is bounded above by a bar which consists anteriorly of the postorbital, and 

 posteriorly, in all probability, of the supratemporal. Hence the postfrontal and 

 supramastoicl do not communicate as they do in the Ichthyopterygia ; and the large 

 foramen above the superior bar has different boundaries below from that observed in 

 Ichthyosaurus, but is like that of the Anomodonta. Hence I call this foramen the 



FIG. 3. 



Fig. 3. — Mosasaurus sp., suspensorium of os quadratum of right side, one-tliird nat. size ; from Greensand of 

 New Jersey. A, from front ; B, from behind ; C, fractured end of proximal half seen at fracture, Or-b ; Exo, exoccipi- 

 tal ; Pe, petrosal ; Pao, paroccipital ; Sts, suture for supratemporal; QA, articular surface for quadrate ; FO, fenestra 

 ovale ; VIII, foramen for eighth nerve ; a b, line of fracture. 



supratemporal foramen, and the bar the supratemporal ba)\ In Sphenodon the par- 

 occipital and supratemporal are fused together. The supramastoid is fused either 

 with the supratemporal or the parietal (Fig. 9, PI. II, and Fig. 3, PI. lY). 



. In the Ptthonomorpha and Lacertilia the zygomatic arch of the Rhyncho- 

 cephalia has disappeared, leaving the superior or supratemporal arch only. That this 

 is truly the supratemporal arch and not the supramastoid is shown by the fact that 

 its anterior connection is with the postorbital as in Sphenodon, and not with the post- 



