THE MAMMALIA OF THE UINTA FORMATION. .'349 



but two calcaneal fticets, the Inferior and susteiftacular being confluent ; the variants 

 in these facets, seen In- comparing a large number of astragah, arc found to be : 

 (1) The greater or less union of tliesc fixcets, looking towards a more primitive Ibrin 

 in which they were probably separate ; (2) the presence of a small ridge, r, at the point 

 of junction, looking towards the well-developed ridge in the later forms (//^racWo/i). 

 The c a 1 c a n e u m presents a very long slender tuber, three astragalar facets and an 

 extremely narrow and deep distal cuboidal facet. The cuboid is corresjwndingly 

 narrow and elongate, in the small species compressed in the middle, and with no trace 

 of a facet for mt, v and little or no contact inferiorly with mt. iir. The ectocu- 

 n e i f o r m is elevated and has a lateral facet for mt. ir. The m e s o c u n e i f o r m 

 is small : according to Cope, "the en t o c u ne i for m is large, flat and posterior 

 in position." * 



TrijAojms (Xo. 10,397, Prince. Coll.). Although the pes as a whole is very nar- 

 row and slcndei', the trochlea is much shallower than in the equine series (Diag. 11, 

 Plate XI, Fig. i>); the cuboidal contact narrows anteiiorly to a point, but the navicu- 

 lar is excluded from contact with the calcancum; the inferior and susteutaeular 

 facets are cither confluent or closely api)io.\imatcd and vary in the development 

 of the ridge (r). Tlie calcaneum has a narrow and oblique cuboidal facet, a 

 long latei'ally compressed tuber and narrow sustentaculum ; there is no trace of a 

 fibular facet. The cuboid is compressed in the middle as in Jli/racJu/us, elongate 

 and with a relatively small distal facet for mt. iv, indicating that this digit was 

 niiicli reduced. The navicular is very deej) and laterally com])re.sse(l. The meso- 

 cuneiform and cntocuneiforin are wanting in the Princeton collection. The ccto- 

 cunciforra articulates with mt. hi only, indicating that the metapodial aiticulation 

 was absolutely plane; the lateral toes were rotated backwards precisely as in Anchi- 

 iherium. 



IIijraco(h>n\ (No. 10,31)7, Princeton Coll.). lu this genus we liiid an e.\aet rejie- 

 tition of the tarsus of Ilyrachijiis in considerably heavier form than in IVi/iIopits, and 

 with few modifications. The a s t r ag a 1 u s has the same limited cuboidal contact ; 

 the three calcaneal facets arc nearly confluent, the "sustentaiMilar" and '"iuferior" 

 are fidly so and a sharp ridge at their point of junction interlocks will: a corresiujud- 



• Tertiary Vcrtebmta, p. '>,59 ; U. niminii. 



f On the Skull <) tlif Eofx-nt; I{liliiori;ro», Orth loynodon, siiul tlic Kcliition of llii>» Qfnim to ollirr Urcmhcrs nf tin' 

 Group. £. M. Museum Bull. No. 3, 1833, p. 17, "llymrodon was a sli'ndvr, lonK-1>>nl><'<l and Hlj^'litly Imili aniinat 

 Willi a long ni;<k and delicate hi'iul. Its prnportionii were IIiohc of a llorsr rallicr than of a Kliiiiori-rog." p. 20, " Fir 

 short, it wa.-< a fursoriul llhinn<;i!ro.«, and all il.i mndiflmlions went towards n<l:iptin[; it lo nwifl iMconiiilinn • • • 

 One can hardly help believing that had this line |H!rsLsti-d, it would have resulted in a iinidigitui type, junt ax the triduc 

 lyl Anfhilfurium of the Mioeene has tcnniiintcd in the Horse." — W. B. Scott. 

 A. P. S. — VOL. XVI. '.hi. 



