534 THE MAMMALIA OF THE UINTA FORMA TIOIST. 



a characteristic of the Ungulata and primitive Mammalia generally has been hitherto 

 ovei-looked. Cope has observed it in Bathiiodon^ and in Peript[icJius ;t Marsh has 

 described it as present in about one-half the Uintailierium asti'agali.J Lemoine§ has 

 found it in all the Cernajsien mammals, which aie of about the same age as the 

 Puerco. It is also present in Ectoconus, MevJ soother lum, Pantolarnhda, and in many 

 if not all of the Puei'co creodonts. The astragalus had a short neck articulating 

 distally mainly with the navicular by an oval and strongly convex facet, and, while 

 in several Puerco genera (^Periptychns, Pantolamhda), it has a considerable ecto- 

 lateral facet for the cuboid, this facet was probably absent in the most primitive 

 forms. Another important feature was the articulation with the calcaneum by two 

 facets only, the ectal (posterior) and sus tentacular (see i-*/(ertaco(:Z«s, Diagram 

 10). 



The tibiale. || A careful comparison of the tarsus of PeriptycJius and Den- 

 droliyrax has brought out the interesting fact that there is a broad ental facet upon 

 the astragalus in some of the Taxeopoda for the tibiale similar to that in the Hjn-a- 

 coidea. This facet, which Cope has recognized as the tibiale or " internal navicu- 

 lar " in PeriptycJius, is also observed in Meniscoilierium, Pantolambda, and the Puerco 

 mammals generally. It has been pointed out by Baur in Uiatatherium, by Cope in 

 Bathmodon, and should undoubtedly be added to the list of primitive characters of 

 the jjes. 



The calcaneum resting upon the ground with its sustentaculum bore the whole 

 weight of the leg transmitted through the astragalus, articulated distally by a 

 concave facet with the cuboid. The cuboid supported mts. iv and v, the three sub- 

 equal cuneiforms articulating respectively with mts. i, ii and iii. A very constant 

 feature was the relative shortening of the mesocuneiform (Phenacodus), so that 

 the proximal portion of the mt. ii was inserted between the endo- and ectocunei- 

 forras. A similai- facet may be present between mt. iii and the cuboid ; these ectal 

 facets being analogous to those upon mcs. ii and rii in the manus in not being of a 

 supporting character; in other words, there was no true displacement between the 

 podium and metapodium. 



The Manus. There was in all probability a cent rale occupying the same posi- 

 tion as in Ilyrax, for this clement has now been found both in the Hyracoidea and 



* Ti:rliaiy Vc-rtclirata, p. 551. 



t Op. cit., p. 399: "This Ibraiucn is foriufil by the closing of llio usual tendinous uoteh, " etc. 

 I Dinoeerata, p. 148. 



§ Various pa]iers upon tlu' Cernaysien fauna. 



1 Baui-, On llu' Morpliology of llie Tarsus in tlie Mammals, Amerieau Naturalist, .Tan., 1885, p. 349. See also, 

 Marsh, Dinoeerata, p. I-IG. 



