PROCEEDINGS OF THE NATIONAL MUSEUM 

 Table of comparative measurements 



VOL. 77 





Type of 



Palaeons- 



cincus 



rugosidens 



Type of 



Edmontonia 



longiceps 



Type of 



Panoplo- 



saurus 



mirus 



Greatest length of skull, in straight line 



Mm. 

 470 

 340 

 145 

 187 

 240 



1 150 



185 



64 



Mm. 



490 



290 



110 



150 



210 



118 



165 



70 



50 



32 



50 



Mm. 

 355 



Greatest breadth iust back of orbits _ 



294 



Breadth of beak, anterior end_- _ _ 



121 



Greatest breadth of beak._ _ _ _ _ 





Breadth of paroccipital processes 



Length of quadrate -_ ___ 





Distance between distal ends of quadrates . _ _ 





Greatest length of orbit _ _ _ 



66 



Vertical diameter of orbit _ 



47 



Greatest diameter of foramen magnum 



Transverse diameter of occipital condyle 



40 

 57 



58 

 58 



1 Estimated. 



Lowe?' jaw. — The right ramus is preserved almost in its entirety 

 as shown in Figure 3. Its outstanding peculiarities of structure 

 are the great depth of the posterior third ; the brevity of the post- 

 coronoidal portion ; the curved dental row ; and the short, inwardly 

 curved sj^mphysial end. It probably includes all of the elements 

 common to the ramus of the predentate dinosauria but in this 

 specimen most of the sutures are fully fused so that the separate 

 elements of the jaw can not be differentiated. 



Much of the outer and lower surface of the ramus, except at the 

 posterior end, is covered by a thick dermal bone which effectually 

 conceals most of the underlying elements. The keeled nature of 

 this dermal bone is well shown in Plate 3. The dermal plate is 

 everywhere fully fused to the underlying bones. The armor does 

 not cover the posterior end of the ramus and here the posterior 

 mandibular elements can be seen. The angular-surangular suture 

 remains distinct from the posterior border to the point where it 

 passes beneath the overlying armor. It shows the angular to have 

 a greatest posterior depth of 42 millimeters, but this rapidly dimin- 

 ishes as the bone passes forward. All of the sutures of the in-' 

 ternal side of the ramus are obliterated through fusion. The 

 dentary, which constitutes fully two-thirds of the entire ramus, is 

 roughly rectangular with a much narrowed portion that turns 

 strongly inward to form the symphysis. The alveolar border shows 

 sockets for 21 teeth, the same as in Euoplocephalus tutus, but three 

 more than in the ramus of Edmontonia longiceps. These occupy 

 a space 140 millimeters in extent, indicating the teeth to be slightly 

 smaller than in E. lo7igiceps where 18 teeth occupy a space 155 milli- 

 meters in length. The tooth row forms a sinuous curve that con- 



