348 KANSAS UNIVERSITY SCIENCE BULLETIN. 



the posterior edge of which has a slight groove into which the 

 anterior edge of the hyomandibular fits. Ventrally it articu- 

 lates with the symplectic. Both bones are concave on the 

 articulating surface, so they are probably connected by a car- 

 tilage. Posteriorly it articulates with the preopercular, which 

 fits into the notch on its posterior edge. It also articulates 

 with the opercular on this edge by a rounded projection. 



Metapterygoid. (Plate XXV, Metap.; plate XXXI, figs. 27, 28.) 



The metapterygoid is a thin bone, rather triangular in shape, 

 with the edges a little convex. The base of the triangle corre- 

 sponds to the base of the bone. The outer face is striated, very 

 thin anteriorly and thickened posteriorly. The posterior edge 

 is grooved to receive the anterior edge of the hyomandibular. 

 This face is concave and is slightly twisted to the posterior at 

 the antero-ventral point. 



The inner face is smooth, is convex dorso-ventrally, and 

 slightly concave along the lower part of the bone. 



Articulations. 



It articulates posteriorly with the hyomandibular. The hyo- 

 mandibular fits into a groove in the posterior edge of the bone. 

 At the lower part it has a slight articulation with the dorso- 

 anterior edge of the symplectic. The anterior edge is free, 

 except at the ventral part, where it is rounded, and articu- 

 lates with the mesopterygoid by overlapping its outer face. 

 Ventrally it articulates with the anterior dorsal edge of the 

 quadrate. The anterior part of the articulation is merely the 

 thin edges meeting, but at the posterior part of the articula- 

 tion both bones thicken and are concave on the articulating 

 surface. 



Symplectic. (Plate XXV, Sym.; plate XXXV, fig. 57.) 



This is a wedge-shaped, triangular bone, with the base of 

 the triangle placed dorsally. The faces are fairly smooth and 

 are not in any way marked. The anterior edge is beveled at the 

 expense of the outer face and is slightly grooved. The pos- 

 terior edge is irregular. With the bones in position only about 

 two-thirds of the symplectic can be seen from the lateral view 

 of the skull, the other third being sheathed in the quadrate. 

 On the inner side all of the bone can be seen. It fits in a 

 wedge-shaped notch on the dorsal posterior edge of the quad- 

 rate and is firmly fixed there, about two-thirds of the bone 

 being in this sheath. 



