610 



CONDYLARTHRA. 



plantigrade, but Phenacodus was digitigrade. The carpus and 

 tarsus (Fig. 321) are very similar to those of Procavia (Fig. 

 290) ; the bones of the two rows are usually serially arranged 

 and the navicular articulates laterally with the cuboid. The 

 astragalus has a neck and convex distal surface, and resem- 

 bles that of 

 theCreodonta. 

 The three mid- 

 dle digits are 

 longer than the 

 outer, and the 

 axis of the limb 

 traverses digit 

 No. 3 as in Pe- 

 rissodactyla. 

 The terminal 

 phalanges are 

 expanded and 

 pointed and 

 must have car- 

 ried hoof-like 

 nails. The 

 femur has a 

 third trochan- 

 ter — another 

 perissodactyl 

 feature. Ulna 

 and fibula are 

 separate and 

 complete, and 

 the fibula ends 

 freely as in 

 C a r n ivora. 

 The tail ap- 

 pears to have been of some length. They were probably 

 omnivorous animals and they varied from the size of a tapir 

 to that of a fox. 



This appears to be a central group with affinities to the 

 Creodonta, Perissodactyla, and to the Hyracoidea. Affinities 

 to the Insectivora and Primates have also been claimed by 



Fio. 321 — Hyracops socialis Marsh. Lower Eocene, Wasatch. 

 A left maims, B left pes (after Marsh, from Woodward). R 

 radius, U ulna, s scaphoid, I lunar, p pisiform, ce centrale, tm trape- 

 zium, td trapezoid, m magnum, u unciform, ca calcaneum, a astra- 

 galus, n navicular, c6 cuboid, 1, 2, 3 cuneiforms, x epicuneiform. 



