64 THE ROYAL SOCIETY OF CANADA 



access to all the type material it would be impossible for the present 

 writer to express a definite opinion; nor is the discussion of the 

 question the object of the present paper. 



The genus Centrosaurus, as established by Lambe, is applied to 

 those horned dinosaurs in which the fontanelle of the frill lies wholly 

 within the parietals (?), in which epoccipitals are developed, and in 

 which a pair of hook-like processes extend backwards and inwards 

 from the posterior border of the frill. The genus Monoclonius, with 

 Mcnocloniiis crassus, Cope, as the type, fails to conform with this 

 definition, particularly in that the backwardly directed processes have 

 not been found in the species. Whether this feature is of generic 

 value or whether Brown was justified in reading it into his re-definition 

 of the genus Monoclonius need not be discussed here. The present 

 writer prefers to retain the genus Centrosaurus until definite evidence 

 is forthcoming that it is identical with Monoclonius. He is also 

 prepared to accept Lambe's contention that Monoclonius flexus is a 

 synonym for Centrosaurus apertus. 



The specimen now mounted in the Royal Ontario Museum, 

 Toronto, .was found by the museum expedition of 1919 in the bad 

 lands of the Belly River formation on the Red Deer river. Alberta, 

 at a point about a mile south of the river and two and a half miles 

 above Happy Jack ferry, at an elevation of 116 feet (aneroid) above 

 the water. 



The animal had fallen on its right side on a bed of blue clay and 

 had been rapidly entombed in sand. At the time of discovery erosion 

 had destroyed the rear of the body, leaving only the head, 17 verte- 

 brae, the scapula, coracoid, and humerus of both sides, the radius 

 and ulna and the manus of the left side, and both sternal bones. 

 The head has the mandible in place and is remarkably perfect through- 

 out. 



The skeleton merits a brief description as it shows for the first 

 time any portion of the body of the species and reveals the nature 

 of the coronoid bone and the character of the thyrohyals. That the 

 skeleton belonged to a comparatively young animal is indicated by 

 the distinctness of the sutures, the separation of the epoccipitals and 

 epijugals, and by the fact that its dimensions are somewiiat less than 

 those of the type. 



Unfortunately Lambe has not published a description of the 

 skulls which he identifies as belonging to Centrosaurus apertus but 

 has contented himself with a photographic reproduction. Brown, 

 however, has given a somewhat detailed, description of Monoclonius 

 flexus with measurements. 



