362 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxxv. 



to Dryj)tosaurus and that figured by Osborn as belonging to Creo- 

 saurus and Allosaurus. There is a similarly placed vacuity in the 

 skull of Diplodocus, whose nasal openings are located far toward the 

 rear of the skull. Inasmuch as this vacuity in the Theropoda and in 

 Diplodocvs appears to be wholly in the maxillary bone, it might be 

 well called the maxillary vacuity. On the left side of the skull of 

 our specimen of Ceratosaurus no actual opening is seen through the 

 bone, but on the right side, near the front of the depression, 47 mm. 

 behind the nostril, there seems to be a foramen. 



Baur stated ° that there was a foramen between the outer surface 

 of the quadrate and the quadra tojugal, as in Sphenodon. The pres- 

 ent writer has not observed this. Seen from behind there is a con- 

 siderable depression where this foramen might be expected to occur; 

 but the bone, though thin, seems to be continuous. 



The articular surface of the quadrate is about 65 mm. wide, but it 

 is short fore and aft. It may be said to consist of two convexities 



Fig. 4. — Ceratosaurus nasicornis. XJ. Inner face of left mandible. 1. Angular; 

 2, Supraanoular ; ■"., Articular; 4, Splenial ; 5, Dentary. 



separated by a broad groove running obliquely outward and back- 

 ward. 



The left, ramus of. the lower jaw (fig 4) permits examination of 

 both faces, but it has been somewhat restored and in places the sutures 

 are not distinct. The right ramus remains attached to the matrix 

 and presents only the outer face. Fig. 3 shows distinctly that the 

 bones of its hinder part have been somewhat displaced. The supra- 

 angular (fig. 4, numeral 2) is seen to form the upper border of the jaw 

 behind the dentary, extending forward above the lateral foramen in 

 the jaw. The angular, 1, is seen beneath the foramen. Its hinder end 

 has probably been broken off, but the bone probably did not reach the 

 angle of the jaw. The relations of this bone to its neighbors was 

 probably the same as shown by Lambe's figure, 6 except that the bone 

 regarded by him as the hinder end of the dentary is almost certainly 

 the angular. In Ceratosaurus the angular continues forward a little 

 in front of the foramen. Here its outer face is overlapped by a pro- 

 cess of the dentary, 5, while on the lower border of the jaw a process 

 of the splenial, 4, presses itself between two processes of the angular. 



" Ajoaer. Naturalist, XXV, p. 446. 



6 Contrib. Canad. Palteont., Ill, Pt. 3, pi. vm, fig. 20. 



