66 



THE CERATOPSIA 



parts at the rear on either side, extending a short distance in front of the limit of the gape. From 

 this we conceived the idea that the same thing would be true of the Ceratopsia, but that the muscular 

 area would extend forward to the anterior limit of the tooth row and so serve, not as cheek pouches, 

 which Hatcher thought might have existed, but merely to retain the chopped food that would other- 

 wise be lost out of the mouth. Incidentally, these are the masseter muscles which also serve in masti- 

 cation and for which there is abundant indication on the bones of the jaws themselves. 41 ' 



Integument 



In restoring the external surface, recourse was had to a cast of the skin impression of Chasmo- 

 saurus received from the National Museum of Canada at Ottawa, and more particularly to the skin 

 which is preserved with the type of Centrosaurus cutleri (PI. Ill, B) in the American Museum. 

 From the latter dies were cut which could be applied to the soft outer layer of plasteline, leaving a 

 positive imprint comparable to that of the hide itself. The integumentary impression, as preserved 

 in the C. cutleri over the flank and over the lower end of the femur, consisted of "small polygonal 

 tubercles and large round tubercles, all low and of the same height. The small tubercles are five or 

 six-sided, close set together and do not grade in size up to the larger, round ones as they do in 

 Ceratops [Chasmosaurus]. . . . The large tubercles are defined by a circumscribing groove and are 

 uniformly round; they were disposed in rows over a part, probably the ventral surface of the 

 body." 47 The disposition of these larger tubercles elsewhere is a matter of conjecture and we have 

 shown them in more or less regular rows over the entire animal with the exception of the face. The 

 wrinkling of the inelastic skin has been suggested by various modern reptiles. 



CHASMOSAURUS 



While a number of skulls of this interesting genus are known in several museums, three skele- 

 tons also have been mounted, two in Ottawa, and one in Toronto. The last has not as yet been 

 described or figured, and while it is a praiseworthy attempt, many of the bones themselves, especially 

 the posterior presacral vertebrae, are so badly distorted by crushing that they could not be articulated 

 with one another. The Ottawa specimens (described by Sternberg), 48 on the other hand, are much 

 more normal and give a very accurate idea of the general morphology of the skeleton, especially as 

 each one supplies supplementary information which the other lacks. The two animals are approxi- 

 mately the same size, though varying slightly in proportions, as the measurements show. 



The two skeletons (PI. XIV, B) stand side by side, one being No. 2245 G.S.C., collected in 

 1913, and the other No. 2280 G.S.C., collected in 1914. The former is of especial interest in that 

 it constitutes the paratype of Chasmosaurus belli as described by Lambe 49 in 1914, the partial skull 

 being figured at that time. 



SKULL 



The skull of Chasmosaurus departs very widely from that of both Centrosaurus and Trkeratops, 

 and resembles that of Torosaurus in the character of the crest. The entire skull is longer and wider 

 but less deep than that of a Centrosaurus, although the over-all length of the two animals is nearly 

 the same, e.g., C. flexus (Y.P.M.) 17 feet 8 inches, Chasmosaurus (No. 2280 G.S.C) 16 feet 3 inches. 

 The muzzle in front of the nasal horn is notably longer and shallower, and the same is true of the 

 low, flat, crest. The latter is broadly quadrangular, with very long squamosals, longer than in any 

 genus other than Pentaceratofs and Torosaurus. The fenestrae are correspondingly large. The 

 epoccipitals are normal, and there are no enlarged spine-like processes as in the contemporaneous 



46 Lull, R. S., 1908, p. 389. 



47 Brown, B., 1917, p. 305. 



48 Sternberg, C. M., 1927. 



49 Lambe, L. M., 1914, B, Pis. XIX-XX. 



