METRIOEHYNCHUS. 151 



squamosal pass into one another by a sharp curve, which forms the postero-external 

 angle of the supratemporal fossa. 



The postfrontal (po.f.) forms the greater part of the postorbital bar, separating the 

 orbit from the supratemporal fossa and forming an incomplete postorbital wall. At its 

 upper end it is overlapped by the lateral process of the frontal in a V-shaped suture, 

 and in this region its posterior edge helps to form a floor to the front part of the supra- 

 temporal fossa, as described above, uniting with the corresponding plate of the frontal 

 and apparently also with the anterior prolongation of the alisphenoid. The outer face 

 of the anterior part of the bone in many species is sculptured like the prefrontal. 

 Posteriorly it is smooth, and overlaps the zygomatic process of the squamosal in a long 

 oblique suture. Immediately behind the orbital part of its border it is produced down 

 into an angular process which unites with a corresponding process on the upper edge 

 of the jugal, thus closing the lateral temporal fossa in front. 



The quadrate (q.) is a massive bone very firmly fixed among the adjacent elements. 

 It consists of an articular region which is directed downwards, outwards, and back- 

 wards and terminates in the condylar surface for the mandible. This surface consists 

 of two convexities, separated by a deep groove running obliquely inwards and forwards 

 from about the middle of the posterior border. The outer edge immediately above the 

 outer condyle bears an elongated oval surface for union with the posterior end of the 

 quadrato-jugal. Above this the outer edge is prolonged obliquely forwards and 

 upwards to the squamosal, along the lower edge of which it extends forwards so as to 

 form a short union with the postfrontal. It also sends back along the ventral face of 

 the squamosal a process which makes an acute angle with the ascending process; the 

 angle forms the anterior border of the external auditory opening. The body of the 

 quadrate is prolonged inwards towards the cranial surface of the skull, uniting with 

 the squamosal and epiotic above and probably with the pterygoid at its inner end. It 

 seems to have formed the lower edge of the aperture for the fifth nerve. On its hinder 

 face it is extensively overlapped by the lateral wings of the exoccipital. 



The quadrato-jugal (q.j.) is a small bone which unites with the outer edge of the 

 lower end of the quadrate by means of an expansion bearing an oval sutural surface. 

 From this a short process runs forwards and is overlapped by the hinder end of the 

 jugal; it forms the postero-inferior angle of the lateral temporal fossa. 



The jugal (j.) is a long slender bone. At its anterior end it terminates in a point 

 which is thrust between the hinder end of the maxilla below and the lachrymal 

 above, the union with the latter being a strong straight suture. Behind this it forms 

 the suborbital bar, which is triangular in section and sometimes sculptured on its outer 

 face. On its inner face in this region there is a narrow palatal plate which terminates 

 posteriorly in a strong inwardly directed process ending in a sutural surface, -with 

 which no doubt the transpalatine unites, though unfortunately all the specimens are 



