282 University Geological Survey of Kansas. 



the specimens, owing to the crushed condition of this part, thus 

 making the line of separation indistinct between it and the 

 ethmoid. The orbito- and alisphenoids are also in a much dam- 

 aged condition, so as to render their boundaries only conjectural. 



The orbital cavity was large, and bounded above by a chain 

 of thickened supraorbital bones, and below by a chain of thin 

 suborbitals, which seem to be quite large. Below this there 

 seems to be a sheet of thin membranous bone covering the hyo- 

 mandibular and the bones of the palato-quadrate arch. The 

 sclerotic ring is composed of two pieces, which are found in 

 place in one of our specimens. The outer borders of these are 

 very heavy, but become thin internally and form a slight ring, 

 which is extended inward. 



Just below the suborbital ring there is a long, thin bar of 

 bone which rests on the superior border of the maxilla, and is 

 covered with minute canals leading inward. This I take to be 

 the same bone called a " supernumerary bone" by Cope, 43 and 

 an " extraknochen " by Crook. 44 It seems to me that both of 

 these authors have been in error in regard to this bone, and 

 that it is the jugal. Crook thought that the jugal was found 

 just beneath this, and has it so marked in the figure of his skull 

 of Xiphactinus , 45 but I am unable to find any such bone in our 

 specimens. 



PECTORAL GIRDLE AND PINS. 



The pectoral girdle is represented by numerous specimens, 

 some of which are preserved almost complete, thus giving a 

 more correct idea of the form than any of the specimens hereto- 

 fore described. This part was not well understood by the early 

 writers on this form, and it was not until about a year ago that 

 Professor Hay demonstrated 46 that this portion had been de- 

 scribed in an inverted position. 



The girdle is composed of the cleithrum, scapula, coracoid, 

 and precoracoid, of which the first is the largest and the second 

 the smallest and most compact. The cleithrum is a long bar of 

 bone composed of two parts, which are bent almost at right 



43. Cret. Vert. West., p. 194. 45. 1. c, t. XVIII. 



44. Paleontographica, 92, s. 115, 116. 46. Zool. Bull., vol. II, p. 42. 



