Stewart.] etaceous Fish 309 



the hinder border of the expansion, and this, continuing up to 

 the midline, has the appearance of a suture. In the crushed 

 specimen before me there is, along the middle line of the ex- 

 pansion, a break in the bone, but whether due to a fracture or 

 to the parting of the bones along a suture I cannot determine. 

 Possibly the parietals were coossified along the midline." 



As to Crook's parietal, I cannot convince myself that there 

 is any suture cutting off the area assigned to it from that as- 

 signed to the pterotic. I regard as pterotic the whole area ex- 

 tending from the posterior external angle of the skull to the 

 lateral expansion considered by Crook as supraoccipital. (!s 



In one of the specimens before me the portion under consid- 

 eration above is so well marked that there can be no more doubt 

 that the expanded portion called supraoccipital by Crook is a 

 separate and distinct bone, which is not separated by suture in the 

 middle line. The portion called parietal by the same author 

 often has numerous cracks running through it, which will easily 

 lead one to believe that they are sutures. 



The prefrontals are small, triangular-shaped bones which lie 

 below the frontals and give attachment to the palatine, as in 

 Xiphactinus. The postfrontals form prominent processes, and 

 are somewhat irregular in form. They form the posterior 

 boundaries of the orbits, and present grooves externally which 

 support about one-fourth of the upper faces of the hyomandibu- 

 lars. 



The parasphenoid is completely preserved in three specimens. 

 It is more slender than in either Xiphactinus or Tchthyodectes , 

 and is quadrilateral in cross-section, instead of triangular, as in 

 the forms mentioned. The transverse processes seem to be well 

 developed, just back of which there are very thin lateral proc- 

 esses which extend upward to the prootics, just beneath which 

 the bone is strongly bent at an angle of about 55 deg., thus giv- 

 ing a strong upward direction to the anterior portion of the skull. 



The sclerotic ring is unusually large for the size of the speci- 

 men, the distance across the orbit being 37 mm., a distance 



'it?. 5, pi. XVI. Sq. an. I /'--. 



