44 ROYAL SOCIETY OF CANADA 



remains are representatives of species of decidedly primitive character, 

 such as 'are to be expected from the Titanotherium (Lower Oligocène) 

 beds ; others are of a more advanced type, and approach closely to species 

 known to occur in the Middle (Oreodon) and Upper Oligocène beds. 



The'conglomeritic nature of the majority of the Oligocène beds of 

 the Cypress hills accounts for the generally scattered and often worn 

 condition of the fossil remains found there, and the isolated state of the 

 exposures, outcropping for the most part in grassy slopes, adds to the 

 difficulty of gauging the relative development of the horizons repre- 

 sented. 



The writer has lately had the advantage of an expression of opinion, 

 regarding the affinities of the species represented by the horse teeth from 

 the Cypress hills, from Mr. J. W. Gidley, of the United States National 

 Museum, Washington. Mr. Gidley, who for some years has made a 

 special study of North American fossil horses, very kindly examined the 

 specimens described in this paper, and for his valuable advice and 

 help the writer takes this opportunity of expressing his indebtedness. 



Mesohippus westoni. Cope. 

 Plate II, figs. 1, la, lb and Ic. 



Anchitlierium sp. indet, Cope, 1885. American ISTaturalist, vol.xix., 

 p. 16. The White river beds of Swift Current river, North- 

 west Territory. 

 • AnchitUerium westoni, Cope, 1889. Ibid, vol. xxiii, p. 153. The 

 vertebrata of the Swift Current river, II. 



Mesohippus westonii, Cope, 1891. Contributions to Canadian Palae- 

 ontology, vol. iii (quarto), pt. i. The species from the Oligo- 

 cène or Lower Miocene beds of the Cypress hiUs, p. 20, pi. xiv., 

 figs. 1^ 2, 2a. 



Mesohippus westoni, Osborn, 1904. Bulletin Amer. Mus. Nat. Hist, 

 vol. XX., New Oligocène horses, p. 169. 



Mesohippus westoni, Lambe, 1905. American Geologist, vol. xxxv, 

 p. 243, pi. xiv, figs. 1-4. On the tooth-structure of Mesohippus 

 westoni (Cope). 



The type material of this species, from Bone coulée. Cypress hills, 

 consisting of a right upper molar, and two right lower molars in place 

 in a fragment of the mandible, is in the museum of the Geological Sur- 

 vey at Ottawa. 



