114 University of Kansas Geological Survey. 



extremity anteriorly, different from the expanded and flattened 

 extremity in Platecarpus. Altogether, the jugal, as already 

 stated, is a stronger element, with stronger muscular attach- 

 ments, than in either of the other genera. Judging from the 

 differences which these three forms present, it is not at all un- 

 likely that in some forms of the group the jugal may exist in 

 a rudimentary condition, as in Yaranus. ' 



Pterygoid. 



Clidastes. The pterygoid is an elongate bone, with four, more 

 or less elongated, processes. The posterior process is broad, flat- 

 tened, and nearly vertical, with a short, emarginate articular sur- 

 face at the extremity, for union with the inferior, anterior inner 

 part of the quadrate. Its under border is markedly convex dis- 

 tally, the upper border thicker and concave. From the base of 

 this process the ectopterygoid process is directed outward and 

 upward, its posterior border continuous with the superior bor- 

 der of the quadrate process. The process is flattened, oval in 

 the middle, and somewhat dilated at the extremity for union 

 with the ectopterygoid ; it is placed obliquely, so that the an- 

 terior superior border is continuous with the upper inner border 

 of the body of the bone. Directed nearly backward and a little 

 outward is a short, pointed process, which I will call the 

 basisphenoid process, inclosing between it and the quadratal 

 process a deep notch for the articulation of the basipterygoid 

 process of the basisphenoid. On the upper side, at the anterior 

 extremity of this notch, there is a small pit for the inserting of 

 the lower end of the epipterygoid. The anterior process is thin 

 and flattened and unites with the posterior inner angles of the 

 palatines, the free margin continuing on the inner side to a 

 point which is less broadly separated from that of the opposite 

 side than the bones are posteriorly. The teeth are twelve in 

 number — greater than in any other genus of the group. 51 The 

 anterior ones are larger than the posterior, and they are all 

 rather closely crowded together. They are moderately flat- 

 tened, with a distinct carina. They are bordered internally by 



51. Merriam gives the number at twelve to fifteen, but I have never seen more than twelve. 



