338 KANSAS UNIVERSITY SCIENCE BULLETIN. 



Articulations. 



The epiotic has six articulations. The two epiotics do not 

 meet on the median line. In the dry skull they seem to have 

 been united by a cartilage. They articulate with the supra- 

 occipital on the dorsal edge, a thin tongue of bone from the 

 supraoccipital overlapping its dorsal inner edge. They articu- 

 late with the pterotics anteriorly, the surfaces being roughened 

 by ridges and grooves. The ventral and exterior edges articu- 

 late with the opisthotic and the exoccipital. The ventral edges 

 of the epiotics form the dorsal border of the foramen magnum. 



Prootic. (Plate XXIX, fig. 11; plate XXX, figs. 12, 13, 14.) 



The prootics are ventral to the sphenotics, posterior to the 

 parasphenoid and superior to the basioccipital and parasphe- 

 noid, the latter extending posteriorly under it. In shape it is 

 roughly pentagonal but is very irregular in outline, the ventral 

 edge being marked by many serrations. 



Outer Face. (Plate XXX, fig. 14.) 



The outer face is marked by a long, irregular ridge, extend- 

 ing from the posterior superior portion, where it is quite prom- 

 inent, down to the antero-ventral edge. At the middle of this 

 ridge is a large foramen, extending through the bone and com- 

 ing out at the superior edge. This foramen is for a part of the 

 fifth nerve. On the superior anterior part of the bone is an- 

 other protuberance, which aids in forming the pit for the 

 hyomandibular head. 



hiner Face. (Plate XXX, fig. 12.) 



The inner face also is quite irregular. It forms the lower 

 posterior side of the brain-case. On the lower edge of the face 

 is a prominent slit with projecting lips, starting at the middle 

 of the anterior border and curving posteriorly and ventrally. 

 At the posterior edge it opens into a cavity in the bone. The 

 foramen for the part of the fifth nerve may be seen on the ven- 

 tral edge. When the bones are in position the two slits are in 

 juxtaposition, forming a cavity through one bone and into the 

 other at the ventral part of the brain-cavity. 



Articulations. 



The prootic has five articulations : Anteriorly with the para- 

 sphenoid and sphenotic, ventrally with the parasphenoid, poste- 

 riorly with the basioccipital, exoccipital and pterotic. The two 

 prootics touch each other on the median line. 



