-I \ RACOSAURUS VLBERTENSIS 89 



of the trill, which, without them, would compare favourably in relative size with the corresponding 

 expansion in later forms ot the Ceratopsia, such as TficeratOps, in which the orbit is hut slightly in 

 advance ot the mid-length ot the skull. Behind the nasal horn the upper outline is straight, then 

 somewhat depressed near the middle of the crest, finally rising to its highest point at the termination 

 of the [undermost process." 



The parietal tenestrae are irregularly oval in outline, with their longer diameter extending 

 From anterior to posterior and slightly diverging outward. Anteriorly, they approach but do not 

 reach the squamosal suture. Beneath the large nasal horn the nasals are massive, to withstand the 

 heavy strains to which the use of the horn subjected them; a bulky transverse arch is formed by the 

 descending processes, which meet ascending processes from the premaxillaries, while in front, the 

 nasals form a shallow, laterally compressed arch, which descends vertically in a sweeping curve to 

 meet the premaxillaries in advance of the narial openings, after the manner of a flying buttress. 

 The vertical nasal septum supports this arch from beneath and is, as in Monoclonius, contributed to 

 jointly by both nasals and premaxillaries. The septum is not fenestrated, agreeing again with 

 Monoclonius but in contrast to Triceratops. 23 The infratemporal arcade is formed by the quadrate, 

 quadratojugal, and a forward process of the squamosal. The last, together with the jugal, forms 

 the actual limits of the infratemporal fossa itself. 



No skeletal elements attributable to Styracosaurus are known, but presumably, in size and pro- 

 portions, the body and limbs were not unlike those of its contemporaries, Chasmosaurus and 

 Monoclotiius ( Centrosaurus ) . 



Dimensions of the Skull 



(After Lambe 1913, but converted into mm.) 



Maximum length of specimen from midway between the points of the back processes 1S61 mm. 



Greatest breadth of same across the processes 1435 



Length of squamosal from the posterior termination of its free edge to the back margin 



of the jugal 397 



Breadth of same from its lowest point to the top of the squamoso-postfrontal suture 31 1 



Length of nasal horn core as found 251 



Transverse diameter of same, at break 70 



Longitudinal diameter of same, at break ... 98 



Transverse diameter of same, at base Ill 



Longitudinal diameter of same, at base 162 



Length of nasal horn core as restored 552 



Measurements Made from the Skull by R. S. Lull 



From tip of rostral to rear of crest between processes, measured over the curve 1390 mm. 



From tip of rostral to tip of left rear process 1970 



Length of posterior left process 550 



Length of intermediate left process 500 



Length of anterior left process 390 (Calculated) 



Nasal horn on rear margin, actual bone 260 



Nasal horn on rear margin, as restored 580 



Depth of premaxillary 280 



Rostral to supraorbital horn suture 770 



Width over orbits 300 



Width over squamosals, on curve 1000 



Length of left parietal fenestra 265 



Width of left parietal fenestra 210 



en in the several Tricerotofs specimens this is so variable a feature that the perforation may be merely the result of 

 postmortem accident, as the septum is extremely thin. 



