OPHTHALMOSAUEUS. 35 



from the other elements of the mandible. Its inner free surface is convex from 

 above downwards, and also from before backwards in its anterior half; posteriorly it 

 is gently concave in the latter direction. Ventrally the inner surface is produced a 

 little downwards, the inner concave surface {cor.f.) of the expansion receiving the 

 posterior end of the coronoid. The gently concave anteiior face {a.s.) is roughly 

 semicircular in outline, the straight side being external and in contact with the 

 surangular. The posterior end [p-S.) is slightly convex in all directions, and is 

 narrowed below both internally and externally by the surfaces for the coronoid and 

 angular respectively. Looked at from the outer side, the greater part of the face is 

 occupied by a deeply concave facet for union with the surangular, while at the postero- 



Test-fiK. 23. 



/lan fiaf 



^«"^- dnq. 



mx. 



Eestoration of the skull and mandible of Oplithalmosaurus. (About \ nat. size.) 



ctnr/., angular ; art., articular ; h.oc, basioccipital ; dent., dentary ; /., foramen between the quadrate and 

 quadrato-jugal ; j., jugal ; I., lachrymal ; mx., maxilla ; n., nasal ; nar., external nares ; par., parietal ; 

 pmx., premasilla ; po.f., postfrontal ; p.orb., postorbital ; pr./., prefrontal ; q., quadrate ; q.j., quadrato- 

 jugal ; s.ang., surangular; scl.r., sclerotic ring; spl., splenial ; sq., squamosal; St., stapes; sup.t.,. 

 supratemporal. 



inferior angle is another facet for union with the angular, though the most extensive 

 junction with this bone is effected by a roughened surface truncating its inferior 

 border. The articulation with the quadrate seems to have been formed by the anterior 

 face of the articular and the outwardly-turned upper border of the posterior part of 

 the surangular. 



The above account agrees very closely with that given by Gilmore for Baptanodon, 

 and still further confirms the probable identity of that genus with Ophthalmosamiis. 

 Gilmore's figures* given in this second paper should be compared, especially liis text- 

 figures on p. 327 and plate xxxvi. of the work quoted below. 



* "Notes on the Osteology of Baptanodon," Mem. Carnegie Museum, vol. ii. (1906) p. 325. 



f2 



