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 cuneiforms 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 represented by three small phalanges, but in the Giraffe and most Bovidae the bones of these digits are wanting.

Fig. 110. A. Left pes of a Tapir (Tapirus americanus). × 1/6.

B. Right pes of a Rhinoceros (R. sumatrensis). × 1/8.

C. (Cast of) right pes of Hipparion gracile. × 1/7.

D. Right pes of a Horse (Equus caballus). × 1/10. (All Camb. Mus.)

1. calcaneum.5. external cuneiform.
2. astragalus.6. middle cuneiform.
3. navicular.7. internal cuneiform.
4. cuboid.

In the Perissodactyla the pes like the manus is symmetrical about a line drawn through the third digit; this line when continued passes through the external cuneiform, navicular 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 Macrauchenia like the carpus differs from that of other Perissodactyles and resembles that of Subungulates in having the bones arranged in lines with little or no interlocking. The calcaneum resembles that of Artiodactyles in having a small facet for articulation with the fibula. Tapirus (fig. 110, A), Rhinoceros (fig. 110, B) and Titanotherium have a short and broad foot with the usual tarsal bones and three well-developed digits,—a number never exceeded by any Perissodactyle. From this tridactylate limb a series of stages is exhibited by various extinct forms leading gradually to the condition met with in the Horse (fig. 110, D) in which the third toe is greatly developed, while the second and fourth are reduced to slender metatarsals attached to the proximal half of the third metatarsal.

In Chalicotherium and Agriochoerus the pes has the same abnormal characters as the manus, the digits being clawed and the ungual phalanges in Chalicotherium deeply cleft.