OPHTHALMOSAUEUS. 27 



inner border of the bone slopes away from the middle line and it is overlapped to a con- 

 siderable extent by the frontals ; it appears that the parietal may or may not take part 

 in the formation of the pineal foramen. External to the surface for the frontals there is 

 another deeply ridged suture, probably for the prefrontal. The line of union between 

 the parietal and the supraoccipital is a not very well-marked ridge, and the junction 

 of the two bones seems to have been weak, a pad of cartilage probably intervening 

 bet\veen them. The rest of the bones of the skull-roof are badly preserved in all the 



^^/_ ^- 



Text-fig. 16. 



Left postfrcintal o£ Ophihalmosawus : A, from above ; B, from below. (R. 2146, |- nat. size. 



-fr.f., surface of union with the frontal and (?) parietal ; orh.h., orbital border ; ;pr.ff., surface of union with 

 the prefrontal ; sq.f., ditto for squamosal ; t.f.l., border of temporal fossa. 



available specimens, so that they cannot be described in detail. The frontals (text-fig. 15) 

 are small oblong bones, the postero-internal angle being in most cases cut away to form 

 the border of the pineal foramen, which is a large oval aperture ; in front of this they 

 unite in the middle line by a strong suture. Externally they unite behind with the 

 postfrontals, and in front apparently with the prefrontals and nasals. The postfrontal 

 (text-fig. 16) is large ; it widens out towards each end. Its relations posteriorly cannot 



E 2 



