1903.] Osborn, The Skull of Creosaurus. 701 



frontals above, are considered to represent a complex com- 

 posed of the prefrontals and lachrymals: they are surmounted 

 by a stout tuberous process which is deeply excavated on the 

 antero-extemal surface; this process may have supported 

 something in the nature of a low dermal horn. 



Below the condyles the basioccipitals descend abruptly 

 downward and backward; on each side of this downward 

 projection are the apparently inferior plates of the exoccipi- 

 tals. From these inferior plates two still more depressed 

 wings extend downward, which probably represent antero- 

 inferior processes of the basisphenoids for articulation with 

 the pterygoids. 



Lower jaw, — In the lower jaw the articulars, angulars, and 

 dentaries are clearly determinable. The suture between the 

 coronoid and angular is faintl}' detenninable posteriorly, the 

 coronoid being depressed. The convex element extending 

 along the inner side of the dentary but firml}' coalesced with 

 it may represent a presplenial ; if this is truly the presplenial 

 it appears to extend as far forward as the symphysis. There 

 are apparently sixteen alveoli for the laterally compressed 

 lower teeth in the dentary. 



A fuller description of these skulls will appear in a forth- 

 coming memoir. 



