I 2 Departme7it of Vertebrate Palceontology. 



27. Oreodon culbertsoni Leidy. 



Fore and Hind Foot. 



Am. Mus. No. 1287. Cast from the mounted skeleton in the American Museum. 

 Oreodon Beds, White River Formation (Oligocene), S. Dakota. 



Shows a very primitive Artiodactyl foot, the fore foot still 

 retaining a rudimentary thumb, and the lateral digits being 

 less reduced than in any of the more recent Artiodactyls. 



Price, $6. 



Scott, W. B., Beitrage zur Kenntniss der Oreodontidae, Morph. Jahrb., 

 1890, pp. 328, 334, pi. xvi, figs. 27, 28. 



28. Hyaenodon horridus Leidy. 



Fore and Hind Foot. 



Am. Mus. No. 1375. Cast from the mounted skeleton in the American Museum. 

 Oreodon Beds, White River Formation (Oligocene), S. Dakota. 



HycBfiodon was the latest and most specialized of the Creo- 



donts or Primitive Carnivores, and the feet are adapted for 



running, although not so well as in the modern swift-footed 



Carnivora. 



Price, $y. 



Scott, W. B., The Osteology of Hycenodon, Journ. Acad. Nat. Sci. 

 Phila., Vol. IX. 



29. Series of Fossil Horse Feet. 

 Illustrating the Evolution of the Horse. 



The Horses afford the best illustration of the evolution of 

 a race of animals during geological time, commencing in the 

 Lower Eocene as small fox-like animals with several toes on 

 each foot, and ending with the modern Horses, Asses, and 

 Zebras. At least ten intermediate stages are known in the 

 direct line of descent, besides several stages of collateral 

 branches, leading into types which have left no modern de- 

 scendants. Those of which casts are now ready are : 



