268 University Geological Survey of Kansas. 



The premaxilla is large and oval in outline, convex externally 

 and very irregular internally. The bone thickens toward the 

 lower border, where there are alveoli for the large teeth, which 

 are never more than three in number, and even three is an ex- 

 ception. The teeth are acutely pointed at the apex, non-striated, 

 and directed slightly forward. Considerably more than half of 

 the bone is supported on the anterior lamina of the maxilla, 

 and in the larger specimens the posterior union with this bone 

 is usually by a dentate suture. In the smaller specimens the 

 suture is usually an undulating line, which seems to indicate 

 that the dentate character of the suture becomes more evident 

 with the age of the animal. There was no sutural union with 

 its fellow on the opposite side, but, from the tubercular nature 

 of the anterior border in some of the specimens, it seems that 

 there may have been a cartilaginous or ligamentous union be- 

 tween the two. In some of the specimens there are a number 

 of tubercular exostoses just above the alveolar border, but this 

 character is as inconstant as the form of the suture mentioned 

 above. 



The maxilla is a large lanciform bone, much thickened to- 

 ward the anterior end and thin posteriorly. Just back of the 

 premaxilla the alveolar border is rather thin, and contains 

 alveoli for several small teeth, usually four. Back of this the 

 bone swells considerably for the accommodation of several large 

 teeth, which are acutely pointed, non-striate, and vary in cross- 

 section from a cylinder to an oval. Back of this the border is 

 occupied by a varying number of small and medium-sized teeth, 

 the alveoli of which are probably not all filled with functional 

 teeth at once. The bases of all of these teeth are cylindric, or 

 nearly so. 



On the next page is given a table showing the great variation 

 in the size and arrangement of the teeth on both the maxilla 

 and premaxilla. The numbers in the left-hand column are 

 the catalogue numbers of the specimens. 



