350 KANSAS UNIVERSITY SCIENCE BULLETIN. 



Articulations. 



The quadrate has six articulations: Anteriorly with the 

 pterygoid by overlapping it, a notch being cut out of the quad- 

 rate to receive it ; with the mesopterygoid at the anterior dorsal 

 angle, the edges resting against each other ; superiorly with the 

 metapterygoid, the edges meeting; with the symplectic by 

 sheathing it; posteriorly with the preopercular, and ventrally 

 with the mandible. 



Mesopterygoid. (Plate XXV, fig. 1; plate XXXI, figs. 25, 26.) 



This is a thin bone between the metapterygoid and pterygoid. 

 It is expanded at the posterior dorsal part, forming a thin 

 posterior end. Its ventral edge is almost a straight line, but a 

 little convex. The anterior end is quite narrow. The expanded 

 part is quite thin on the edge, and rounds over from the pos- 

 terior to near the center, where it drops down abruptly, making 

 the narrow anterior part. 



The lateral face is concave from posterior to anterior, the 

 posterior part is folded and waved. The inner face is convex, 

 the anterior dorsal edge twisted so that it points out laterally, 

 the ventral edge pointing inward. 



Articulations. 



The mesopterygoid has three articulations, its ventral edge 

 fitting into a groove on the dorsal edge of the pterygoid, pos- 

 teriorly with the metapterygoid. It has a slight articulation 

 with the quadrate. 



Pterygoid. (Plate XXV Pt.; plate XXXV, figs. 57, 58.) 



The pterygoid is a stout bar uniting the quadrate and pala- 

 tine. The anterior end is heavy and triangular in section, the 

 base of the triangle dorsal, its inner edge inclined a little ven- 

 trally. Posteriorly it bends ventrally and laterally, and 

 expands to about twice the depth. The anterior end is nar- 

 rowed down to a rough point which articulates with the pre- 

 frontal. The pterygoid is cut out on the antero-ventral part 

 and also on the lateral part, making an articulation for the 

 palatine. On the dorsal edge the inner part has a deep, angu- 

 lar groove, into which the mesopterygoid is placed, it being 

 grooved also. 



The posterior end of the pterygoid is rather thin and is 

 drawn downward and a little outward. Immediately posterior 

 to the place where it turns down a thin plate of bone extends 



