336 KANSAS UNIVERSITY SCIENCE BULLETIN. 



ExocciPlTAL. (Plate XXXI, figs. 32, 33, 34.) 



The exoccipitals are paired bones in the caudal region of the 

 skull, but also have a place in the sides. The lateral face of 

 the bone is hexagonal, with the longest side placed caudally. 

 Posteriorly it is hour-glass shaped, irregular and narrowed in 

 the middle from the inner side, and the lower edge is cut off 

 transversely at the expense of the inner edge. It forms about 

 five-sixths of the boundary of the foramen magnum. 



Outer Face. (Plate XXXI, fig. 32.) 



The outer face is hexagonal, though far from regular. It is 

 slightly concave, and is marked by a foramen placed almost in 

 the middle of it which extends obliquely through the bone. 

 From this foramen a groove passes posteriorly, bisecting the 

 caudal border. The edges of the outer face are very irregular, 

 being drawn out into numerous points. 



Inner Face. (Plate XXXI, fig. 34.) 



The inner face is irregular, the lower posterior part articu- 

 lating with the cervical vertebrae. It points downward and in- 

 ward. The middle of the inner face is marked by two fora- 

 mina, one extending obliquely through it to the middle of the 

 outer face ; the second is posterior to it. The openings to these 

 foramina are in a depression. On the superior posterior por- 

 tion of the face there is another protuberance, which is pointed 

 posteriorly, starting at about the middle of the inner face and 

 articulating with the epiotic. 



Articulations. 



The exoccipital has six articulations: Ventrally with the 

 basioccipital ; anteriorly with the basioccipital and the prootic ; 

 superiorly with the pterotic and epiotic and with the other ex- 

 occipital. 



Basioccipital. (Plate XXX, figs. 20, 21, 22, 23.) 



The basioccipital is a very irregular bone. It has five faces 

 to consider. 



Posterior Face. (Plate XXX, fig. 20.) 



The posterior face of the basioccipital is concave and is 

 marked by a number of concentric rings. Slightly above the 

 center of the concavity there is a small pit. This part of the 

 bone articulates with the neck vertebrae. The longest axis ex- 

 tends dorso-ventrally. 



