THE OSTEOLOGY OF THE DIADECTIDAE 131 



nal meatus, the orbits, and the nares. The quadrate region with 

 its opening is similar in all important particulars to the same region 

 in specimen No. 1078. The quadrate bone is a little longer, but, 

 as it has been impossible to free the region from all matrix, minor 

 details are uncertain. The orbits are oval, longer than high, and 

 look directly outward. The lower edge projects rather more than 

 the upper, and can be seen if the skull is viewed directly from 

 above. The antero-posterior diameter of the orbit is 0.045 111 ; 

 the vertical diameter, 0.032™. The nares are nearly circular and 

 located at the extremity of the skull. They are placed obliquely, 

 so that they look outward and forward. The posterior and lower 

 walls are continued funnel- wise, the opening being in the upper ante- 

 rior corner of the nostril. 



The quadrate region has the greatest vertical extent of any por- 

 tion of the skull, making the postorbital edge of the skull, jugal, 

 and quadrato-jugal descend abruptly as a flange, covering the 

 posterior portion of the jaw. The whole length of the lower edge 

 of the skull is sharply concave, reaching its greatest height just 

 anterior to the orbit and then descending slightly to the anterior 

 end. The anterior end of the nose overhangs the lower jaws con- 

 siderably. 



Viewed from the front or rear, it is seen that the skull is much 

 narrower than the jaws; the sides of the postorbital portion slant 

 outward as they descend, so that the wall of the skull is oblique. 

 The supraoccipital region is depressed between two projections 

 of the posterior angles of the skull formed by the squamosal, or 

 possibly even by an epiotic, though this last-mentioned bone cannot 

 be made out. Its possible presence is inferred as possible from the 

 condition of the Pariotichidae, where Cope reports its presence. 



There are two small openings, the post-temporal foramina, on 

 the posterior face of the skull near the outer edge. These open 

 directly upon the petrosal and the upper face of the pterygoid, so 

 that their enlargement would produce exactly the condition of the 

 Chelonidae among the turtles. 



The total length of the skull from the anterior end of the nose 

 to the posterior end of the slightly projecting lower jaws is nearly 

 o.2 m . The height across the skull and lower jaws is 0.125 111 oppo- 

 site the parietal foramen. 



