342 KANSAS UNIVERSITY SCIENCE BULLETIN. 



terior to the articulation witii the frontal, the expanded edge 

 drops rapidly and forms an acute projection on each side, ex- 

 tending toward the front ; anterior to these the edge continues 

 regular. This anterior part of the parasphenoid extends for- 

 ward as a projection. The upper part is marked by a thin 

 ridge extending along the median line. This projected anterior 

 end of the parasphenoid flares out inferiorly, the part articu- 

 lating with the vomer being wider than the upper surface. The 

 groove between the upper edges of the parasphenoid is quite 

 deep and narrow. 



Faces. 



The faces of the parasphenoid are rather smooth but marked 

 by fine striations. At the posterior part of the expanded upper 

 edge there is a sharp ridge, pointing posteriorly, and ex- 

 tending to the ventral edge ; immediately posterior to the ridge, 

 on the superior edge, there is a foramen of some size, extending 

 into the bone anteriorly. 



Articulations. 



The parasphenoid has eight articulations. The anterior part 

 articulates ventrally with the vomer, laterally with the pre- 

 frontals and anteriorly with the ethmoid. On the rest of the 

 dorsal edge it articulates with the following, in order : frontal, 

 alisphenoid, sphenotic, prootic and basioccipital. 



Frontal. (Plate XXV, fig. 1; plate XXVI, fig. 2; plate XXVII, fig. 3; 

 plate XXIX; plate XXXI, fig. 35; plate XXXII, fig. 36.) 



The frontal is unpaired, and is the largest bone in the skull. 

 Its superior edge is drawn out at the posterior part into a thin 

 crest. Anteriorly it widens out laterally. The ventral surface 

 has two wings articulating with the corresponding upward 

 growth on the parasphenoid. The frontal has three faces, a 

 postero-lateral, a dorsal, and the anterior beveled faces. 



Lateral Face. (Plate XXXI, fig. 35.) 



The lateral face is at the posterior half of the bone. From 

 the thin dorsal edge it is inclined outward and posteriorly, ar- 

 ticulating with the sphenotic. A rounded ridge extends up 

 from this articulation to the anterior edge of the face, where 

 it fades out. This face is marked with striations. 



Dorsal Face. (Plate XXVII, fig. 3; frontal.) 



The edges are gently concave, the face narrowing at the 

 anterior end. A ridge extends along the median line of 



