[parks] CENTROSARUS APERTUS 59 



uppermost is apparently absent on the right side. In the left bone it 

 is situated 32 mm. down and back from the lower edge of the external 

 mandibular foramen. 



Measurements of Sur.\ngular 



Upper point to postero-inferior point 225 mm. 



Oblique width of lower thickened portion 46 " 



Point between coronoid process and angular to posterior extremity 60 " 



Thickness of upper flange 17 " 



Vertical height 156 " 



In lateral external view the angular is relatively high in front but 

 is just perceptible below the surangular in the rear. The external 

 face is slightly concave and the inferior face almost flat. The external 

 inferior angle is distinctly rugose. There are two small foramina 

 near the suture with the dentary and three near the centre (only two 

 on the left side). 



Measurements of Angular 



Length along external face 77 mm. 



Suture with dentary 20 " 



Suture with splenial 108 " 



Suture with surangular 68 " 



Height externally 49 " 



Length, inferior 110 " 



Width, inferior 50 " 



The dentary conforms to the general pattern seen in the Cera- 

 topsia. The drawings (Plates II and III), together with the measure- 

 ments given below, will serve for its description. The internal dental 

 foramina are not well preserved but their presence is indicated by a 

 broken line. The foramina on the external face of the bone are as 

 indicated, but it is likely that more occur as the surface was somewhat 

 injured. 



The coronoid process is very stout with a sharp hook forward 

 at the upper end and with a very pronounced outward bulge near the 

 base. Its thickness at this point, measured horizontally, is 54 mm. The 

 inner surface shows a sharp ridge running down and back against 

 which the coronoid is set. The upper edge is distinctly corrugated. 



The sutures between the coronoid process and the coronoid and 

 surangular are clear and open. The posterior margin of the coronoid 

 process is irregular and is excavated at the point where the external 

 mandibular foramen enters the surangular. 



