146 University of Kansas Geological Survey. 



liquely inwards. The outer posterior one, forming about one- 

 half of the glenoid fossa, is largely concave, and is produced 

 into a prominent ridge outwardly. The posterior inferior bor- 

 der is thickened, concave, and roughened immediately back of 

 the glenoid margin, straight and thin distally, ending in a 

 rounded angle. The anterior superior border is nearly straight 

 or gently convex on the outer three-fifths, moderately thickened 

 and ending in a rectangle. Proximally it is beveled convexly 

 at the expense of the outer surface, terminating-in a thin, sharp, 

 prominent ridge, extending from the apex of the roughened tri- 

 angular space in front of the scapular surface to the inner side 

 of the superior border, a little before the middle. The inferior 

 border is thin and convex throughout from before back, the 

 convexity being greater on the posterior part. The border is 

 lipped for cartilage, and is a little thicker near the posterior 

 end. Just back of the anterior fourth of the border there is a 

 deep emargination, with very thin margins. In front of this 

 emargination the border of the bone is thicker, especially on the 

 posterior half, where the border is swollen. Just back of the 

 emargination the border is also a little thickened. About mid- 

 way between the bottom of the emargination and the margin of 

 the scapular articulation the small coracoid foramen pierces the 

 bone from above downwards. 



In most specimens of Mosasaurs from Kansas the bones are 

 flattened, from pressure. The present specimen has, however, 

 the two bones but little changed, so that the angle between the 

 scapula and the coracoid is shown nearly as in life. Their re- 

 lationship will be clearly seen in plate xxxi, figure 6, which 

 shows the two bones as articulated, from behind. 



Platecarpus. The coracoid of Platecarpus resembles that of 

 Clidastes rather closely. The bone is longer and less expanded 

 distally, the neck longer and proportionally narrower, the pos- 

 terior margin longer and concave throughout. 



In Tylosaurus, the coracoid is very large in proportion to the 

 scapula. The anterior border is nearly straight, the posterior 

 concave, the inferior strongly convex. There is no emargina- 

 tion . 



