Ilambe] cretaceous GENUS STEGOCERAS 27 



Externally along the parieto-frontal mass from the posterior 

 border to the midline in front are five suturai facets of which the 

 posterior three are occupied in the specimen by a squamosal, a postof- 

 bital and a postfrontal. Between the postfrontal and the anterior 

 end of the specimen are other suturai facets for elements which were 

 not recovered with the specimen. The hindermost of these is nearly 

 square and apparently indicates the position of a prefrontal. The 

 whole of the suturai surface from here forward probably denotes the 

 full extent of the contact of the nasal bone with the frontal. 



Viewing the specimen from below, the frontal portion antero- 

 externally enters largely into the formation of the roof of the orbital 

 cavity; axially it covers the brain from the parieto-frontal suture 

 forward, and is in suturai contact with the presphenoid, the orbito- 

 sphenoid, and the alisphenoid. In the surface supplied to the roof 

 of the orbital cavity are a number of foramina, of variable size, the 

 outer openings of canals debouching obliquely to the surface and 

 directed radially outward. The parietal moiety anteriorly forms the 

 hinder part of the roof of the brain-cavity, and is in contact with the 

 alisphenoid and farther back with the otic mass, the exoccipital and 

 the supra-occipital. Externally, on either side, it roofs over the inner 

 portion of the large cavity which has the supratemporal fossa as. its 

 posterior exit above to the upper surface. 



Squamosal. This bone is considerably broader than long, is 

 thick and substantial with a rugose upper surface which is sharply 

 defined from its nearly equally roughened, vertical borders. The bone 

 forms the postero-external angle of the skull and enters into the 

 formation of the supratemporal fossa to the extent of one-half of the 

 margin of the opening. 



On the upper surface of the skull the squamoso-postorbital 

 suture runs directly outward from the supratemporal fossa, and the 

 squamoso-parietal suture inward and backward from the same opening 

 to the posterior border. 



Inferiorly the squamosal sends a stout process forward under the 

 mid-breadth of the postorbital, the latter being deeply channelled to 

 receive it. Posterior to this process the bone thickens downward 

 and in this thickening is the socket for the head of the quadrate. 

 The line of junction with the postorbital, parietal and supra- 

 occipital is very distinctly shown in this aspect. In advance of the 

 posterior border is an inframarginal area extending outward from the 

 supra-occipital and parietal and curving downward to where the 

 bone thickens in advance of its postero-lateral angle. This area 

 represents the amount of the posterior overhang of the squamosal. 



