THE SKELETON IN MAMMALIA. THE PES. 523 



phalanges have the contiguous sides flat, and the axis of the limb 

 passes between them, and between the cuboid and navicular. 

 The astragalus has both the proximal and distal surfaces 

 pulley-like, and articulates with the navicular and cuboid by 

 two facets of nearly equal size. The calcaneum articulates 

 with the lower end of the fibula if that bone is fully developed. 



In the Suina four toes are developed, and though in the 

 Peccaries the third and fourth metatarsals are united, they 

 are all distinct in most members of the group, as are all 

 the tarsal bones. In the Hippopotami the four digits are of 

 approximately equal size, and the middle ones do not have 

 the contiguous faces of their ungual phalanges flattened. 



In the Tragulina the cuboid, navicular, and two outer cunei- 

 forms are united forming a single bone ; all four metatarsals 

 are complete and the two middle ones are united. In the 

 Tylopoda and Anoplotherium commune only the third and 

 fourth digits are developed, their metatarsals are free distally, 

 but are elsewhere united. In the Ruminantia the cuboid and 

 navicular are always united and so are the second and third 

 cuneiforms, while in Cervulus all four bones are united 

 together. The third and fourth metatarsals in Ruminants 

 are always united in the same way as are the third and fourth 

 metacarpals, while the second and fifth are always wanting. 

 In Deer the second and fifth digits are usually each repre- 

 sented by three small phalanges, but in the Giraffe and most 

 Bovidae the bones of these digits are wanting. 



In the PERISSODACTYLA the pes like the manus is symme- 

 trical about a line drawn through the third digit; this line 

 when continued passes through the external cuneiform, navi- 

 cular and astragalus. The astragalus has its distal portion 

 abruptly truncated, and the facet by which it articulates with 

 the cuboid is much smaller than that by which it articulates 

 with the navicular. The calcaneum does not articulate with 

 the fibula. The tarsus in Macrauckenia like the carpus 

 differs from that of other Perissodactyles and resembles that 



