[lambe] 



FOSSIL HORSES OF THE OLIGOCENE 



SI 



The foregoing species described in this paper are related to or 

 resemble previously described species from Montana and Dakota as 

 follows : — » 



M. westoni, Cope. 



M. prœcocidens, / 



sp. nov. 1 



M. propiiiquiis, I 



sp. nov. I 



M. brachystylus, f 



Osborn \ 



M. stenolophus, 



sp. nov. 



{ 



M. planidens, / 



sp. nov. \ 



M. assiniboiensis, / 

 sp. nov. t 



More primitive than M. latidens, Douglass and M. mon- 

 tanensis, Csborn from the Lower 01igocene,Titanotherium 

 beds. 



Nearly related to and more advanced than M. westoni 

 (and ? M. montanensis of the Titanotherium beds). 



Nearly related to and more primitive than M. bairdi, Leidy 

 of the Middle Oligocène, Oreodon beds. 



The type of the species is from the Upper Oligocène, Leptau- 

 cheniabeds. 



Approaches closely M. brachystylus of the Leptauchenia 

 beds. 



Approaches in size M. intermedius, Osborn and Wortman 

 froni the Upper Oligocène, Protoceras beds. 



Some resemblance to but ? larger than M. validus, Osborn 

 of the Protoceras beds. 



It woidd seem probable then that the species from the Cypress hills, 

 in their relative degrees of progressiveness, are to be assigned to the 

 horizons of the Oligocène in the following order : — 



M. westoni / 



M . prœcocidens (. 



M. propinquus 



M . brachystylus / 



M . stenolophus \ 



M. planidens I 



M. assiniboiensis ( 



Lower Oligocène, Titanotherium beds. 

 Middle Oligocène, Oreodon beds. 

 Upper Oligocène, Leptauchenia beds. 



Upper Oligocène, Protoceras beds. 



