158 DINOSAURS OF NORTH AMERICA. 



The nasal bones are more elongate than the frontals, and the suture 

 uniting the two moieties is obsolete. These bones support entirely 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 supported a high, trenchant horn, which must 

 have formed a most powerful weapon for offense and defense. No 

 similar weapon is known in any of the carnivorous Diuosauria, but it 

 is not certain whether this feature pertained to all the members of this 

 group or was only a sexual character. 



The premaxillaries are separate, and each contained only three func- 

 tional teeth. In the genera Compsognathus and Megalosaurus, of this 

 order, each prem axillary contained four teeth, the same number found 

 in the Sauropoda. In the genus Creosaurus, from the American Juras- 

 sic, the premaxillaries each contain five teeth, as shown in PL XII, 

 fig. 1. 



The maxillary bones in the present specimen are large and massive, 

 as shown in PL VIII, fig. 1. They unite in front with the premaxil- 

 laries by an open suture; with the nasals, laterally, by a close union; 

 and with the jugal behind, by squamosal suture. The maxillaries are 

 each provided with fifteen functional teeth, which are large, powerful, 

 and trenchant, indicating clearly the ferocious character of the animal. 

 These teeth have the same general form as those of Megalosaurus, and 

 the dental succession appears to be quite the same. 



Above the antorbital foramen on either side is a high elevation 

 composed of the prefrontal bones. These protuberances would be of 

 service in protecting the orbit, which they partially overhang. 



The orbit is of moderate size, oval in outline, with the apex below. 

 It is bounded in front by the lachrymal, above this by the prefrontal, 

 and at the summit the frontal forms for a short distance the orbital 

 border. The postfrontal bounds the orbit behind, but the jugal com- 

 pletes the outline below. 



The jugal bone is J.-shaped, the upper branch joining the postfrontal, 

 the anterior branch uniting with the lachrymal above and with the 

 maxillary below. The posterior branch passes beneath the quadrato- 

 jugal, and with that bone completes the lower temporal arch, which is 

 present in all known dinosaurs. 



The quadratojugal is an L-shaped bone, and its anterior branch is 

 united with the jugal by a close suture. The vertical branch is closely 

 joined to the outer face of the quadrate. 



The quadrate is very long and compressed antero-posterioiiy. The 

 head is of moderate size, and is inclosed in the squamosal. The lower 

 extremity of the quadrate has a double articular face, as in some birds. 

 One peculiar feature of the quadrate is a strong hook on the upper 

 half of the outer surface. Into this hook a peculiar process of the 

 quadratojugal is inserted, as shown in PL VIII, fig. 1. 



The pterygoid bones are very large and extend well forward. The 



