14 PROCEEDINGS OF THE NATIONAL MUSEUM VOL.87 



both Brown ^^ and Lull," who have found epoccipitals to be distinct 

 ossifications in skulls of Monoclonius flexus studied by them. In a 

 recent letter Dr, Brown says : "In Cope's type of Monoclonius crassus 

 I cannot be sure whether they [epoccipitals] are separate." 



While it is true that many aged individuals of the Ceratopsidae 

 have complete coalescence of the epoccipital bones with the frill, in 

 Brachyceratops we appear to have a type of frill ornamentation whose 

 origin is unlike that of other horned DinosauHa. 



Most of the epoccipital processes are incomplete, as this portion of 

 the frill was protruding from the bank. There were certainly six, 

 possibly seven, of these processes on the border of the interparietal? 

 as contrasted with four on the Monoclonius frill. These decrease in 

 size from above downward. On the left side of the median emargina- 

 tion the first two processes, although incomplete, are abnormal in 

 development, either as the result of a diseased condition or of an 

 old injury. There is no indication of forwardly directed processes 

 at the rear of the fenestra as found in specimens of MonocloniUrS. 



Although none of the borders of the fontanelle are preserved, this 

 specimen demonstrates this opening to be farther removed from the 

 central bar than indicated in the first restoration. Viewed laterally 

 (fig. 11) the interparietal? is more concave from end to end than in 

 the juvenile specimens. 



The anterior median end is almost completely preserved, and it 

 displays the same sutural borders for articulation as those of the 

 juvenile specimen, which have been fully described. 



At the time of describing the detailed skull structure of B. mon- 

 tanensis, following Hay ^^ and von Huene,^^ the median element pre- 

 viously called parietal was referred to as the dermosupraoccipital or 

 interparietal. Since that time two important papers have been pub- 

 lished. Lull's ^* "Eevision of the Ceratopsia" and Sternberg's ^* 

 "Homologies of Certain Bones of the Ceratopsian Skull." The 

 former returns to the use of parietal for the median element but 

 without discussing the dissenting opinions; Sternberg, however, pre- 

 sents arguments based on a further study of the type skull 

 of Styracosaurus alhertensis, in which he attempts to prove this 

 median element of the frill is the parietal, and further dissents from 

 my identification of the postfrontals, which he calls frontals. 

 Although willing to concede that there is reason for a difference of 

 opinion as to my original interpretation of the bones in question, I 



10 Bull. Amer. Mus. Nat. Hist, vol. 33, p. 551, 1914. 



u Mem. Peabody Mus. Nat. Hist., vol. 3, pt. 3, pp. 33, 34, 1933. 



i^Proe. U. S. Nat. Mus., vol. 36, p. 97, 1909. 



isNeues Jahrb., Band 2, pp. 150-156, 1912. 



1* Mem. Peabody Mus. Nat. Hist., vol. 3, pt. 3. 1933 



1" Trans. Roy. Soc. Canada, vol. 21, sect. 4, 1927. 



