On .s-owe Gorgonopsian Skulls. 511 



this feature the skull differs from nil the Gorgonopsia in which the 

 structure of the top of the head is known. The median suture 

 extends the whole length of the top of the skull. Ahout lo mm. 

 in front of the pineal foramen it is crossed by the suture separating 

 the frontals from the parietals, the limits of which bone can lie 

 wholly seen. The parietal is wholly excluded from the border of 

 the temporal opening by the large postorbital which meets the squa- 

 mosal posteriorly. The temporal opening is bounded by the post- 

 orbital and squamosal except for its lower border, which is formed 

 mainly by the jugal. The jugal is a large bone, supported by the 

 maxilla in its anterior third, and overlapped by the postorbital half- 

 way and the squamosal posteriorly. The jugal extends right to the 

 end of the skull, almost touching the quadrate mass. 



The palate is partially displayed. There is possibly a small, narrow, 

 elongate interpterygoid vacuity lyingjust behind the descending flanges 

 of the pterygoids. Immediately anterior to these llanges there is a 

 fairly shallow median groove which passes forward to the bar sepa- 

 rating the internal narial openings. In its posterior half this groove 

 is narrow and its sides are formed of dentigerous keels of the ptery- 

 goids. At the bottom of the groove there is a median suture exten- 

 ding, apparently, from the interchoanal bar to the interpterygoid 

 vacuity. The suture is very evident in the anterior broader portion 

 of the groove where it abuts abruptly against the somewhat spongy 

 bone of the interchoanal bar. In the posterior portion it is not so 

 evident: but there are no signs of any lateral sutures separating a 

 vomer from the pterygoids, and the depth and narrowness of tin 1 

 groove together with its acute dorsal angle would seem to preclude 

 any possibility of a vomer lying in that position. On the other hand, 

 the interchoanal bar has every appearance of being single. It is a 

 spongy bone, sharply separated off posteriorly from the hard bones 

 of the palate. Anteriorly it broadens somewhat and shows the two 

 canals separated by a median keel on the ventral surface; but 

 nowhere is a median suture visible. Posteriorly its meets the 

 pterygoids. 



The occipital plate shows a small triangular foramen magnum: 

 the basioccipital condyle is not so massive as in Arctops wiltistoni. 

 There is a large interparietal with a median keel which is continued 

 almost down to the foramen magnum. The tabnlare is large and 

 lies partly against the parietal and partly against the squamosal. 

 The foramen jugiilare looks almost wholly downwards. The whole 

 occipital plate slopes strongly backwards. The paroccipital process 

 is fairlv broad but thin. 



