20 



MAEINE EEPTILES OF THE OXFOED CLAY. 



rounded articular knob, the lower surface of which bears a rather deep cup-like 

 depression {c[.f.), into which the upwardly projecting postero-external angle of the 

 quadrate is received. As already mentioned, there seems to have been a certain 

 amount of play between the two bones ; and this probably indicates that the rostral 

 portion of the skull was capable of some small degree of movement on the cranial, this 

 movement being transmitted to the quadrato-jugal by the jugal bar. The external 

 face of the bone is overlapped below by the posterior upturned end of the jugal, the 

 surface for which is clearly deiined (see text-fig. 10, K,ji(.f.). Above, the bone bears a 

 roughened facet [jj.orh.f.) by which it joined the postorbital, which also overlapped the 

 upper end of the jugal. 



Text-fiij. 10, 



fiorbf. 



porbf. 



mxf. 



Eight quadrato-jugal and jugal of Oplitlialmosaurus : A, quadrato-jugal, outer side ; B, ditto, lower side, 

 with articulation for quadrate ; C, ditto, inner side ; D, jugal, outer side. (E. 2180, about f nat. size.) 



ju., jugal ; ju.f., facet for jugal ; ?./., facet for posterior end of lachrymal ; mx.f., facet for maxilla ; 

 p.orh.f., facet for postorbital ; g./., facet for quadrate. 



The jugal (text-fig. 10, D) is a long curved bone, consisting of a slender horizontal 

 bar in front and a laterally-flattened, upturned blade behind. Tlie upper portion of 

 the blade overlaps the outer face of the quadrato-jugal, and is in turn overlapped by 

 the lower end of the postorbital (jhorb.f.), so that it is thrust between these two 

 bones. The anterior bar is oval in section in its posterior half, but anteriorly it 

 becomes compressed from side to side, and is deeply grooved [l-f.) superiorly for union 

 with the lower edge of the posterior prolongation of the lachrymal. On the inner 

 side of this region there is an elongated and well-defined surface, which is flat or gently 



