﻿Vol. 64.] BliACHYBHYNCHLS FEOM THE OXFOED CLAY. 351 



measurements of this bone in his description of the last-named 

 species, so that I am unable to compare them with his measurements 

 of Metriorhynchus hrachyrhynclius. 



The sculpture of the frontal region in No. 165 coincides exactly 

 with Deslongchamps's description. The frontal is comparatively 

 smooth, with numerous irregular but superficial pit tings radiating 

 from the centre, while the praefrontals are covered with strongly- 

 marked sculpture of the same nature. In IN'o. 164 this sculpture 

 is greatly intensified, the indentations on the frontal being almost 

 grooves. 



The postfrontal is an exceedingly massive and powerfully- 

 developed bone, widening from its junction with the frontal as far as 

 the anterior and exterior corner of the temporal fossse, at which 

 point it attains a width of 50 millimetres, compared with 30 mm. 

 in M. superciliosus. The bone forms a distinct angle, instead of the 

 slight angle little more than a curve in the same bone of M. super- 

 ciliosus^ thus corresponding to the opposite angle in the prsefrontal. 

 The orbit, owing to the great development of the posterior border of 

 the prsefrontal with its straight edge and the anterior border of the 

 postfrontal, does not show the sinuous curve which is seen in 

 M. su^erciliosus, but has an angular appearance, the two bones 

 mentioned above lying at an angle of 50° one to the other, the angle 

 itself being rounded off by the free edge of the frontal. 



The skull attains its greatest width just behind the posterior 

 corner of the orbits. In No. 164 the width amounts to 300 milli- 

 metres, in No. 165 to 270 ; but, as the bones of the temporal region 

 in the former have suffered considerably from crushing, the latter 

 measurement approximates more nearly to the original width of the 

 skull. 



The parieto-frontal crest is 35 mm. broad at the anterior 

 border of the temporal fossae, decreasing slowly in width towards 

 the parietal region ; at the suture of the frontal and parietals it 

 measures 20 mm. across, from which point it tapers rapidly to some 

 5 mm. in width at a distance of 25 mm. from the back of the parietal 

 ridge ; after that it widens again very quickly, until it attains a 

 width of 30 mm. at its posterior edge. In skull No. 164 crushing 

 has altered the shape. The crest is 150 mm. long. The bones 

 of the back of the skull possess in the same marked degree the 

 massiveness which is so noticeable a feature of the whole skull ; 

 especially remarkable in this respect are the quadrates, which 

 measure in width at their articulating surface 60 mm. In 31. super- 

 ciliosus, 45 mm. is the approximate width for full-sized skulls, and 

 the bones are far less substantial. 



I come now to that which is, in some respects, the most interest- 

 ing portion of the skull, namely, the palatines, pterygoids, and 

 vomers. They are preserved in both skulls more or less, but those 

 of No. 165 are in better condition. In skulls of Metriorhynchus 



Q. J. G. S. No. 255. 2 a 



