Section IV, 1921 [53] Trans. R.S.C. 



The Head and Fore Limb of a Specimen of Cenlrosariis apertus 



By W. A. Parks, Ph.D., F.R.S.C. 



(Read May Meeting, 1921) 



Monoclonius dawsoni was established by Lambe on a fragmentary 

 skull and part of a squamoso-parietal crest from the Belly River beds 

 of Alberta.^ At a later date he recognized that the crest did not 

 belong to the same individual as the skull and redescribed it as the 

 type of a new genus and species, Centrosaurus apertus."^ 



In his monograph on the Ceratopsia, Hatcher quotes Lambe's 

 description of Centrosaurus apertus in a footnote and in the text 

 expresses the opinion that the crest does not belong to Monoclonius 

 dawsoni.^ 



In 1914 Barnum Brown described a complete skull from the 

 Belly River beds of Alberta as Monoclonius fiexus and in his pre- 

 liminary statements returns to the original idea that both the skull 

 and frill first described by Lambe belong to the same species, Mono- 

 clonius dawsoni. If this view is correct Centrosaurus apertus becomes 

 a synonym.^ 



The following year Lambe again returned to the discussion and 

 stoutly maintained the validity of Centrosaurus apertus and its dis- 

 tinctness from Monoclonius dawsoni. He further maintained that 

 Monoclounis fiexus of Brown is a synonym for Centrosaurus apertus. 

 This opinion is based on two skulls in the Victoria Memorial Museum 

 which reveal the entire anatomy of the head and which, in Lambe's 

 opinion, show the full type of frill described by him for Centrosaurus 

 apertus.^ 



Two years later, in 1917, Brown described a complete skeleton 

 of a ceratopsian as Monoclonius nasicornis and an incomplete skeleton 

 as M. cutleri.^ 



From the above summary it is apparent that both the generic 

 and the specific names of Centrosaurus apertus are in doubt. Without 



1 Cont. Can. Palaeontology, vol. 3, pt. 2, 1902, pp. 57-63. 



2 Ottawa Naturalist, vol. XVIII, No. 4, July, 1904. Trans. Royal Soc. Canada, 

 2nd Series, Vol. X, Sec. IV, pp. 3-9, 1904. 



3 U.S. Geol. Sun, Mon. XLIX, 1907, p. 93. 



" Bull. Am. Mus. Nat. Hist., Vol. XXXIII, 1914, pp. 549-558. 



s Geol. Sur. Can., Mus. Bull. XII, May, 1915. 



« Bull. Am. Mus. Nat. Hist., Vol. XXXVII, 1917, pp. 281-300. 



