504 



GEOLOGY OF THE DENVER BASIN. 



Seen from the side, this skull appears lacertilian in type, the general 

 structure being light and open. From this point of view, one special feature 

 of the skull is the large, elevated, trenchant horn-core situated on the nasals. 

 < >ther features are the large openings on the side of the skull, four in 

 number. The first of these is the anterior nasal orifice; the second, the 

 very large, triangular, antorbital foramen; the third, the large oval orbit, 

 and the fourth, the .still larger lower temporal opening. 



The parietal bones are of moderate size, and there is no pineal 

 foramen. The median suture between the parietals is obliterated. The 

 frontal bones are rather short, and are closely united on the median line. 

 The nasal hones are more elongate than the frontals. and firmly coossified. 



Fig. 60.— Skull of Ceratosa i is nasicornis Marsh; Bide view. One-sixth natural size 



a, nasal opening! '' horn-core; c antorbital opening; rf, orbit; e, lower temporal fossa; /, foramen in lower jaw; 

 t, transverst bom 



These bones support the large, compressed, elevated horn-core, on the 

 median line. The lateral surface of this elevation is very rugose, and 

 furrowed with vascular grooves. It evidently supports a high, trenchant 

 horn, which must have formed a most powerful weapon for offense and 



defense. 



The premaxillaries are separate, and each contained three functional 

 teeth. The maxillary hones are large and massive, as shown in fig. 60. 

 The\ are each provided with fifteen functional teeth, which are large, 

 powerful, and trenchant, indicating (dearly the ferocious character of the 

 animal when alive. 



