254 Prof. 0. C. Marsh — ISfeiv Jurassic Dinosaurs. 



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 weapou 

 for offence and defence. No similar weapon is known in any of 

 the Dinosauria, but it is not yet certain whether this feature per- 

 tained to all the members of this family, or was only a generic 

 character.' 



The premaxillaries are separate, and each contained only three 

 functional teeth. In the genera Compsognathiis and Megalosanrus, 

 of this order, each preraaxillary contained four teeth, the same num- 

 ber found in the Sauropoda. In the genus Creosaurus, from the 

 American Jurassic, the premaxillaries each contain five teeth. 



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

 as shown in Fig. 1. They unite, in front, with the premaxillaries 

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

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

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

 powerful, and trenchant, indicating clearly the ferocious character of 

 the animal when alive. These teeth have the same general form as 

 those of Megalosau7'us, 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 pre- 

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

 orbital border. The post-frontal bounds the orbit behind, but below, 

 the jugal completes the outline. 



The jugal bone is ±- shaped, the upper branch joining the post- 

 frontal, tlie anterior branch uniting with the lachrymal, above, and 

 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 quadrato-jugal 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-posteriorly. 

 The head is of moderate size, and is enclosed 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 of the quad- 

 rate, a peculiar process of the quadrato-jugal is inserted, as shown in 

 Fig. 1. 



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

 The posterior extremity is applied closely to the inner side of the 

 quadrate. The middle part forms a pocket, into which the lower 

 extremity of the basi-pterygoid process is inserted. To the lower 



1 The " horn" of Iguanodon described by Mantell, and since regarded as a carpel 

 spine, proves to be the distal phalange of the thumb. 



