28 ROYAL SOCIETY OF CANADA 



three species of Megacerops and one of Symborodon, the hyracodonts by 

 one species of Eyracodon, and the rhinoceroses by two species of Acera- 

 therium. 



Mesoliijppus westoni is known from teeth of primitive character, and 

 is named after Mr. T. C. Weston, to whom the Survey is indebted for 

 so many yearg of faithful service as a collector. Megacerops angusti- 

 genis is based on numerous specimens of upper and lower jaws with 

 teeth with which were associated as probably belonging to the same 

 species certain bones of the skull and limbs affording additional infor- 

 mation. 



The fossil remains from the Cypress hills that Cope identified with 

 Menodus americanus, Leidy and M. proutii, Owen, Norwood and Evans 

 are, in the light of recent research, probably referable to Megacerops 

 coloradensis, Leidy. The results of the exhaustive studies of the Ti- 

 tanotheres made by Professor Osborn of late years are to be found in 

 his papers entitled " The Cranial Evolution of Titanotherium," ^ 1896, 

 and " The Four Phyla of Oligocène Titanotheres," ^ 1902. They form 

 a solid basis for future research, and with them a proper understanding 

 of the group is rendered possible, and a welcome release offered from 

 the almost hopeless confusion into which the literature relating to these 

 mammals had fallen, a confusion arising principally from a multiplicity 

 of synonymous terms. M. selicynianus is a third species, named in 

 honour of Dr. Alfred E. C. Selw\Ti, under whose able direction the 

 Geological Survey of Canada made rapid and substantial progress 

 during many years. Menodus syceras. Cope, is regarded by Osborn as 

 probably identical with Symhorodon acer, Cope. The material on which 

 M. syceras was based consists of pairs of coossified nasal bones that 

 exhibit characters siuch as are found in the corresponding bones of 

 8. acer. 



The ancient rhinoceroses from this region are Aceratherium occi- 

 dentale (Leidy) represented Iw a fragment of a right mandibular ramus, 

 and A. mite (syn. A. pumilum, Cope in part). 



The type specimen of A. (Ccenopus) pumilum. Cope, consisting of 

 the anterior end of a jaw holding deciduous teeth, has been shown by 

 Osborn^ to belong not to an Acerathere but to an Hyracodon, \dz. : 

 Hyracodon nehrascense, Leidy. The cotype of A. pumilum, which is of 

 necessity now to be regarded as the type, establishes, according to the 

 same authority, the identity of A. pumilum with A. mite. Cope, of the 

 Symborodon or Titanotherium beds of north-western Colorado. 



' Bulletin. American Museum of Natural History, vol. viii., article ix., 

 p. ra. 



' Ibid, vol. xvi., article viii., p. 91. 



* Memoirs of the American Museum of Natural History, vol. I., part III., 

 "The Extinct Rhinoceroses, by Henry Fairfield Osborn, New York, 1898. 



