mabhh.] CERATORAURUS. 157 



new type of vertebra as strange as it is unexpected; and a third is seen 

 in the pelvis, which has the bones all coossified, as in existing birds. 

 Among adult birds Arclmeopteryx alone has the pelvic bones separate, 

 and this specimen of Ceratosaurus is the tirst dinosaur found with all 

 the pelvic bones anchylosed. The metatarsal bones are also coossi- 

 fied, a feature characteristic of birds, but not known hitherto in any 

 dinosaur. 



THE SKULL. 



The skull of Ceratosaurus nasieornis is very large in proportion to 

 the rest of the skeleton. The posterior region is elevated, and mod- 

 erately expanded transversely. The facial portion is elongate, and 

 tapers gradually to the muzzle. Seen from above, the skull resembles 

 in general outline that of an alligator. The nasai openings are sepa- 

 rate and lateral, and are placed near the end of the snout, as shown in 

 PI. Till. 



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 elevated, trenchant horn core, situated on 

 the nasals (PL Till, fig. 1, b). Another feature is the large open- 

 ings 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. A fifth aperture, shown in the top view of 

 the skull (PI. VIII, fig. 3, h), is the sirpratemporal fossa. These open- 

 ings are all characteristic of the Theropoda, and are found also in the 

 Sauropoda, but the antorbital foramen is not known in any other 

 Dinosauria. 



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

 slopes backward. The quadrates are strongly inclined backward, thus 

 forming a marked contrast to the corresponding bones in Diplodocus 

 and other Sauropoda. The occipital condyle is hemispherical in gen- 

 eral form, and is somewhat inclined downward, making a slight angle 

 with the long axis of the skull. The basioccipital processes are short 

 and stout. The paroccipital 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 nearly in their original position. 



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

 men. The median suture between the parietals is obliterated, but 

 that between these bones and the froutals 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. 



