26 



MAEINE EEPTILES OP THE OXFOKD CLAY. 



and of a process running outwards and backwards to meet the squamosal, with which 

 it unites in a strong complex suture ;. the upper surface of this process is convex from 

 before backwards, the ventral concave. The upper surface of the body of the bone is 

 strongly convex from side to side ; posteriorly the outer border is produced downwards 

 to the side of the brain-case, while anteriorly it bears on its lower edge a deep 

 groove into which probably the upper end of the epipterygoid fitted. The inner side 

 bears a flat sutural surface for union with the corresponding bone of the opposite side : 

 this sutural surface consists of a comparatively narrow posterior portion and a broad 



Text-fig. 15. 



Part of upper region of skull of Oplithdlmosaurus, sbowiug the squamoso-parietal bars and tlie 

 skull-roof with the parietal foramen. (E. 3535, | uat. size.) 

 /)-., frontal; pa., parietal ; p.for., pineal foramen ; post.f., postfrontal ; sq., squamosal. 



oval roughened anterior region, which is borne on the inner end of a prominent ridge 

 which crosses the cranial surface somewhat obliquely, dividing it into distinct anterior 

 and posterior halves. The posterior half is about as broad as long, concave in all 

 directions, while the anterior is narrower and gently concave fi-om before back only. 

 It appears that this ridge formed a sort of tentorium across the roof of the brain-case, 

 and probably marks the line of separation between the optic lobes and the cerebral 

 hemispheres, the farmer probably being very large. In front of the median suture tlie 



