Trof. 0. C. Marsh — Neiv Jurassic Dinosaurs. 253 



This interesting fossil is quite distinct fi'om any hitherto described, 

 and, as it represents a new genus and species, may be called Cerato- 

 saurus nasicornis. It also belongs to a new family, which may be 

 named the Ceratosauridce. 



The skeleton, which is almost perfect, is over seventeen feet in 

 length by actual measurement. The animal when alive was about 

 half the bulk of the species named by the writer AUosauriis fragilis, 

 which is from the same geological horizon. A second skeleton, 

 some parts of which, also, are here described, is referred to the latter 

 species. 



The Skull. — The skull of Ceratosaurus nasicornis is very large, 

 in proportion to the rest of the skeleton. The posterior region is 

 elevated, and moderately expanded transversely. The facial portion 

 is elongate, and tapers gradually to the muzzle. Seen from above, 

 the skull resembles in general outline that of a crocodile. The 

 nasal openings are separate, and lateral, and are placed near the end 

 of the snout, as shown in Fig. 1. 



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 (Fig. 1, &). Another feature is the large 

 openings on the side of the skull, four in number. The first of these 

 is the anterior nasal orifice (a) ; the second, the very large triangular 

 antorbital foramen (c) ; the third, the large oval orbit (d) ; and the 

 fourth, the still larger lower temporal opening (e). A fifth aperture, 

 shown in the top view of the skull, is the supra-temporal fossa. 

 These openings are all characteristic of the Theropoda, and are 

 found also in the Sauropoda, but the antorbital foramen is not known 

 in any of the other Dinosauria. 



The plane of the occiput, as bounded laterally by the quadrates, 

 is inclined forward. The quadrates are strongly inclined back- 

 ward, thus forming a marked contrast to the corresponding bones in 

 Di'plodocus, and the other Sauropoda. The occipital condyle is 

 hemispherical in general form, and is somewhat inclined backward, 

 making a slight angle with the long axis of the skull. The basi- 

 occipital processes are short, and stout. The par-occipital processes 

 are elongate and flattened, and but little expanded at their extremities. 

 They extend outward and downward, to join the head of the quadrate. 



The hyoid bones appear to be four in number. They are elongate, 

 rod-like bones, somewhat curved, and in the present specimen were 

 found near their original position. 



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

 foramen. The median suture between the paiietals is obliterated, 

 but that between these bones and the frontals is distinct. 



The frontal bones are of moderate length, and are closely united 

 on the median line, the suture being obliterated. Their union with 

 the nasals is apparent on close inspection. 



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 



