443 



[Copp 



tion, which are typified in the Condylarthra, the ProhoHndea, the Aiuhhj- 

 poda and the Artiodactyla resiiectivel3\ (Figs. 5-9.) 



Fig. 9. 



Fig. 10. 



Fig. 9.— Hind foot of PoSbrotherium labiatum (original). 



Fig. 10.— Fore leg and foot of Hyracotherium venticolum (original). 



Orders. — From tlie preceding considerations we derive the following 

 definitions of the primary divisions of the Ungulata, which should be 

 called orders. In the first place I find the diversity in the structure of the 

 carpus to be greater ifl the relations of the magnum and scaphoides, than 

 in the relations between the unciform and the lunar. In other words the 

 trapezoides and magnum are more variable in their proportions than is the 

 unciform. This is directly due to the fact that the reduction of the inner 

 two digits is more usual than the reduction of the external tAvo. I there- 

 fore view the relations of these bones as more characteristic. In the tarsus 

 the really variable bone is the cuboid. It is by its extension inwards 



PROC. AMER. PHILOS. SOC. XX. 112. 3d*, PRINTED NOVEMBER 17, 1882. 



