132 University of Kansas Geological Survey. 



Just below the proximal end of the coronoid an elongated 

 foramen leads into the upper part of this cavity. 



The surangular forms the outer anterior three-fifths of the 

 cotylus, the surface strongly concave antero-posteriorly, gently 

 convex from side to side. Posteriorly on the outer side, the 

 bone unites obliquely with the articular, and from back of the 

 middle with the splenial, which forms the inferior border of the 

 mandible here. The upper border, as far as the coronoid, is 

 thin and sinuous. The extremity is broad and oblique, fimbri- 

 ated or roughened. On the anterior half, the lower border is 

 narrowly and deeply grooved for the reception of a tongue from 

 the splenial. Posteriorly and internally to this groove, there is 

 another for the reception of the margin of the articular. On 

 the inner surface, below, the bone is excavated for the reception 

 of the flattened part of the articular, its upper margin being an 

 angular margin or ridge reaching about midway. Above this 

 process a groove leads down into an excavation, which is broader 

 in front, forming a foramen leading into the cavity between the 

 articular and surangular. The upper border in front is thick- 

 ened and rounded for the reception of the coronoid, with a 

 sharp, thin, sinuous margin on the outer side posteriorly. Just 

 balow the surface for the coronoid near the anterior margin, 

 there is a groove leading into a foramen. The lower margin of 

 the bone is suturally united with the splenial and the angular, 

 as already described. 



The splenial of Baur, the angular of authors, forms the thick- 

 ened and rounded lower border of the bone for more than half 

 the distance back of the articulation. At its distal extremity it 

 has an oval, vertical, articular surface, convex in both direc- 

 tions, for union with the presplenial. The bone is U-shaped in 

 cross-section, the outer lip with a narrow tongue for insertion 

 into the surangular, the inner one thin and overlapping the 

 angular, but not reaching to the coronoid. In the cavity 

 between the two the plate-like process of the articular is re- 

 ceived. See plate lxiii. 



The coronoid has its upper border deeply concave antero- 

 posteriorly, convex and rounded from side to side. It is U-shaped 



