CL. 



THE ANCESTORS OF THE HORSE AND ITS RELATIVES COMPARED IN SIZE 

 AND FORM WITH THEIR TYPICAL MODERN REPRESENTATIVE 



a, Hyracotherium of the Lower Eocene ; b, Plagiolophus, or Orohippus, 

 of the Middle Eocene ; c, Mcsohippus> of the Oligocene ; d, Mcrychippus> of 

 the Miocene ; e, Pliohippus, of the Pliocene ; /, the Horse, Equus caballus. 



