THE OSTEOLOGY OF THE DIADECTIDAE 135 



case. Consequently no separate description can be given of the 

 exoccipital, paroccipital, opisthotic, or petrosal. Cope reported 

 that the opisthotic and paroccipital were separate in Empedias 

 and Chilonyx (Cope, 1896), but I can find no trace of a separation 

 in the specimens here described. 



The quadrate. — This bone both in form and relationships is 

 best compared with those turtles which have the quadrate open 

 posteriorly. The rugose bones of the skull roof terminate abruptly 



Fig. 6. — The quadrate region of specimen No. 1078. q = quadrate, ?>.s = basi- 

 sphenoid, &o = basioccipital, exo + po= exoccipital and paroccipital. 



in the quadrate region, leaving an oval opening with its greatest 

 axis vertical and open below. To the anterior and upper edge of 

 this opening is attached the edge of the smooth quadrate, thus 

 forming a conspicuous line of demarkation. The quadrate is 

 approximately half funnel-shaped, pitching in on the upper, lower 

 and anterior sides toward the center of the space. At this point 

 the bone terminates by rounding in toward the center of the skull, 

 leaving the posterior portion of the space open as the entrance of 

 an opening to the interior of the skull. The upper part of the 

 posterior edge of the quadrate is curved slightly downward, form- 

 ing a hook. The lower portion of the quadrate is expanded into 

 two articular faces which correspond to the articular faces of the 



