272 



University Geological Survey of Kansas. 





MANDIBLES. 



No. 



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287 

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The articular portion as described by Hay 28 is composed of the 

 derm and antarticulars, but I am incliDed to think that this 

 author was somewhat mistaken in the extent of the last of these 

 elements, as he says in the description of this part : "Relying 

 on two good specimens of Xiphactinus and one of Ichthyodectes , 

 I am confident that the proximal end of the antarticular is con- 

 tinuous with the long, sword-shaped process described by Cope, 

 and that this process is entirely distinct from the dermarticu- 

 lar." Professor Cope states 29 that the articular is distinct, short, 

 and irregularly wedge-shaped, and supports half of the cotylus. 

 In this Professor Cope was correct, as the antarticular is not con- 

 tinued forward in a long, sword-shaped process, but is separated 

 from this portion by a suture, which is indistinct in many of 

 the specimens, and it is probably owing to this fact that Hay 

 was unable to find it. 



The dermarticular is a large bone, and in most of the speci- 

 mens it supports less than one-half of the cotylus. On the ex- 

 ternal side it is exposed for some distance beyond the cotylus, 

 when it is covered by the dentary, and continues forward on 

 the internal side, as a long sword-shaped process, for nearly 

 two-thirds the length of the jaw. The cotyloid process is promi- 



28. Zool. Bull., vol. II, No. 1, p. 37. 



29. Cret. Vert. West, p. 191. 



