154 The Ottawa Naturalist. [Feb. 



border, is a little over one-third of its length. The angular enters 

 largely into the exterior surface of the jaw posteriorly, its 

 sutural junction with the dentary having much the same general 

 direction as in Ceratops canadensis. Its external surface is much 

 farther forward beneath the base of the coronoid process than in 

 Triceratops. I he surangular, articular and splenial are pre- 

 served and will be described at a later date. The coronoid 

 process is strong and terminates anteriorly above in a narrowlv 

 rounded hook. The height of the alveolar border above the 

 lower margin of the dentary decreases only slightly from front 

 to back, and in this respect the direction of the border differs 

 materially from that of C. canadensis, otherwise there is a general 

 resemblance in the mandible of these two species. The lower 

 teeth bear a very high keel, and the grinding surface, as display- 

 ed by those teeth which have been in use, is almost vertical. 



The dorsal surface of the skull of Chasmosaurus is rather 

 smooth throughout. Small vascular markings occur on the 

 parietals behind the inclined platform and on the platform itself. 

 The upper surface of the postfrontals show these grooves to a 

 greater extent but not in so decided a manner as the supra- 

 orbital horn-cores and the epoccipitals which are the most rugose 

 parts of the skull. 



The skull has been prepared, as it appears in the figures, 

 by its discoverer, Mr. Charles H. Sternberg, and his son, Mr. C. 

 M. Sternberg. 



Measurements. Feet. Inches. 



Estimated length of skull from midw T ay between 

 apices of parietal epoccipitals to front edge of 



rostral bone, about 5 5 



Length of skull along median line from posterior 



parietal border to anterior end of dentary 4 7 



i vimum breadth of crest 3 51 



Breadth between centre of orbits 11 



Breadth between lower margin of lateral temporal 



fossae 1 



Antero-postcrior diameter of supraorbital horn- 

 core near base J i 



Transverse diameter of same near base 2 



Length of same, tip restored 5| 



Length of squamosal from front end of process 

 under lateral temporal fossa to back termina- 

 tion 2 



Length of coales< ed parietals along median line 

 from posterior border to front edge of raised 

 portion between supratemporal fossae 2 6 



