Stewart | Cretaceoun Fishes. 279 



articular surface near the anterior extremity, which probably 

 gives attachment for a preorbital bone. 



The prefrontals are stout bones, and are especially character- 

 ized by the presence of a large anterior facet for articulation 

 with the malleolar portion of the palatine. In the figure of the 

 skull of Xiphactinus, as given by Crook, :,! the prefrontals are 

 represented as extending well backward and forming a portion 

 of the anterior and superior rim of the orbit. In this I am in- 

 clined to think that he was in error, for in several more or less 

 disarticulated skulls in the collection I find that this supposed 

 posterior portion of the prefrontal is a distinct bone which has 

 become separated, showing a well-marked suture where it 

 united with this bone and the frontal. This bone is the supra- 

 orbital mentioned above, and is rather thick and lunate in 

 outline. 



The parietal bones have been much in doubt by most authors, 

 probably owing to the fact that this portion of the skull is often 

 much distorted and crushed, thus obliterating many of the 

 sutures, or making them so indistinct as to render them un- 

 recognizable. 



Cope first thought that the supraoccipital might represent 

 the conjoined parietals, :!7 but concluded later ::s that this was not 

 the case, and that the bones he had called epiotics were the 

 parietals. Crook states that the parietals are completely sepa- 

 rated in the median line by the supraoccipital, 3 ' 1 but seems to 

 have been somewhat in doubt about the exact extent of these 

 bones, as the anterior portion is but poorly defined in his figure 

 of the specimen on plate XVIII. Professor Hay has described 

 them 4 " as wedge-shaped narrow bones which lie between the 

 anterior ends of the pterotics and the posterior ends of the 

 frontals, probably meeting each other in the median line, and 

 including the elevated granular portion assigned by Crook to 

 the supraoccipital, in which I think he is right. If we ex- 

 amine a well-preserved skull of Ichthyodectes we will at onco 



36. Paleontojaaphica, 1892, pi. XVII. 39. Paleontographica, 1892, p. 115. 



37. Crrt. Vfrr . ; 40. Zool. Bull., vol. II. pp. 28< 2'.<. 



38. I.e.. p. 188. 



