OPHTHALMOSAUEUS. 23 



frontal and prefrontal bones. The inner face of the bone, which is concave from above 

 downwards, is marked by a series of longitudinal ridges running forwards from the 

 nasal opening. 



The maxilla (test-fig. 13) is a small bone compared with the premaxilla and in no 

 case seems to have borne teeth, though the dental groove begins in its anterior 

 portion. The bone, as a whole, is a shuttle-shaped structure, with the upper and 

 inner surfaces deeply concave from above downwards. The posterior prolongation 

 bears on its outer face (text-fig. 13, A) an elongated concave, grooved surface {ju.f.) for 



a' d^. 



Eight maxilla of Oplithdlmosaurus : A, outer side ; B, upper side ; C, iuner side ; D, vertical section 

 at the line D-D in fig. 0. (E. 2180, i nat. size.) 



d.c;., dental groove; f.p., facial portion of bone; ju.f., facet for jugal ; l.f., facet for lachrymal; 

 nar.h., border of external nares ; n,f., facet for nasal ; 2^1.2^., palatine plate ; ]pmx.f., facet for premaxilla : 

 p.p., processes on palatine border. 



union with the overlapping jugal : there may have been a little play between the two 

 elements. In front of this the outer face of the bone is flat above and gently convex 

 below : its upper border is produced upwards into a blunt triangular process, the outer 

 face of which is overlapped by the lachrymal, with which it unites in a short strong 

 suture {l.f.) along its upper edge. In front of this projection the upper border of 

 the bone is rounded and forms part of the lower edge of the nasal opening {nar.h.). 

 Anterior to this, again, there is an elongated and roughened facet («•/•) for union with 



