540 THE MAMMALIA OF THE UINTA FORMATION. 



discovered ceiitrale.* The distinctive features of the tarsus have long been recog- 

 nized, viz., the extension of the navicular with the astragalus above the cuboid, and 

 the fibulo-calcaneal facet. 



4. TOXODONTIA. 



Piof Copef has found a striking resemblance to the proboscidian pes in Toxo- 

 (lon. The astragalar and fibular facets of the short c a 1 c a n e u m are subequal and 

 face upwards, the cuboid facet is on the inferior face of the extremity of the calcan- 

 eum and faces downward. The astragalus has probably no cuboid facet; its 

 navicular facet is plane and truncates the bone somewhat inferiorly as Avell as distally. 

 The metapodial elements are robust and short, the distal metatarsal keels are poste- 

 rior and rudimental ; the proximal faces have lateral facets indicating a slight dis- 

 placement. The number of digits is uncertain, the lateral ones are reduced in 

 length, but robust. " The posterior feet were more truly jjlantigrade for the extrem- 

 ity of the calcaneum reached the ground." The instep was raised, forming an arched 

 angulate type of foot. If this description is correct, this foot is more primitive than 

 that of the Proboscidia. 



.I. Mackauchenia. 



The feet of Macraudlienia have some striking peculiarities. The lateral displace- 

 ment in the carpus and tarsus so characteristic of all the Perissodactyla is absolutely 

 wanting in the tarsus and aberrant in the carpus. As Burmeister pointed out in his 

 most recent paper J (p. 263) a gap exists in the usual point of junction of the calca- 

 neum, cuboid, astragalus and navicular. The astragalus is entirely separated from 

 the cuboid and even from the calcaneum, the navicular participating in this 

 separation. Ilis description and figures strikingly suggest the arrangement of the 

 tarsals of the dog in this region. The calcaneum has but two astragalar facets, 

 the sustentacular and inferior having coalesced, as in some species of Pahaotliermm, 

 liliinoceros, and the Hyracodontidaj ; its distinctive feature is the extensive fibular 

 trochlea, very similar to that in the Artiodactyla, and functionally unlike those 

 observed in the primitive Equus and Titanotherium series. The c a r p u s is also 



* Kiitimeyer, op. cit., pa.nc 11, loot-note. 



fNotc on the atnictnre of the I'osterior Fool in Toxodon. Proo. Am. Philos. Soo., April, 1881, p. 403. 



:t Neuc Beobiicliliin.ijun un MiicranclK'niii Pattichonica. Nova Acta der Ksl. Loop. -Carol. Dculsclu'n Akadoniie 

 dor Naturforschcr, Bd, XLVII, Nr. 5, (ip. 239-207 (Nachtriigliclie Beschreibung dor Fusswurzel von Macrauchenia). 

 Also, Dcscriiicion do la Macrauchenia Patachonica. Ann. del. Mus. Piilil., Buenos Ayres, Tom. i, p. 32-GG. 



