90 BULLETIN 110, UNITED STATES NATIONAL MUSEUM. 



surangular. It would apiDear that some of the posterior end of the right element 

 in this individual is missing, for its homologue of the opposite ramus extends more 

 posteriorly and laps underneath the prearticular, but ends considerably short of 

 the posterior end of the ramus, as in Tyrannosaurus. It extends forward of the man- 

 dibular foramen, being overlapped on the external side by the dentary. On the 

 internal side, as Hay has pointed out, a posterior process of the splenial "presses 

 itself between two processes of the angular." The angular has a limited exposure 

 on the inner side of the jaw where it passes beneath the prearticular below the 

 mandibular foramen. 



Surangular (sa.). — The relationship of the surangular to contiguous elements 

 so far as they can be determined is very similar to those conditions observed in 

 the Antrodeinus ramus. Vertically it is considerably narrower than in Antrodemus, 

 but, as in that genus, when the jaws are closed its upper border passes up inside the 

 quadratojugal bar, as shown in figure 2, plate 17. 



Splenial (sp.). — The splenial is a deep lamellar bone that is applied to the 

 inner side of the dentary and supradentary. It is perforated near its inferioi 

 margin on the anterior half by a foramen, as shown in figure 55. This foramen 

 probably functions the same as the large oval foramina present in the splenial of 

 both Tyrannosaurus and Alheriosaurus. In the present specimen the splenial is 

 only to be observed in the ramus of the left side, and its damaged condition renders 

 an accurate description of the bone impossible at this time. Its posterior limits 

 are only traceable on the lower posterior side, where it sends backward a finger- 

 like process to articulate with the angular. Its lower margin is here visible for a 

 short distance on the external side. 



Nowhere does the splenial form the inner parapet of the alveoli as would be 

 inferred from the outline figure of the Ceratosaurus ramus as figured by Hay.' 



At a point slightly posterior to the last alveolus the upper margin of the 

 splenial sweeps downward below the border of the supradentary, much as the 

 splenial sweeps downward below the border of the supradentary as in Tyrannosaurus, 

 though the ventral deflection of this margin is more gradual than in the latter 

 genus. The anterior end of the splenial is missing but in all probability it termi- 

 nates in a tapering process as in the other Theropods, and it has so been indicated 

 in figure 3. 



Coronoid. — ^The coronoid though undoubtedly present in Ceratosaurus has 

 not as yet been recognized as a distinct element. 



Articular (ar.). — The articular is small and compact, and forms the greater 

 part of the cotylus, which is obliquely transverse and bifossate. It is overlapped 

 on its inner and under sides by the prearticular, and on the outer side by the 

 surangular. Unfortunately the posterior extremities of both articulars in this 

 individual are missing, and in the restored skull, shown in figure 33, this portion 

 of the articular has been restored after Antrodemus. 



Prearticular (p. ar.). — ^The prearticular is only to be observed in the left ramus, 

 and this one lacks its anterior end. In so far as one may judge from the parts 

 preserved it is very similar to that of Antrodemus. Hay^ discusses this bone as 

 follows : 



• Proc. U. S. Nat. Mus., vol. 35, 1908, fig. 4, p. 362. ^ Loc. cit., p. 363. 



