482 THE MAMMALIA OF THE UIN^TA FORMATION. 



the shaft is transvcrsel}' extended and quite massive, expanding but little into the 

 distal end. The articular surflices for the astragalus are quite deeply incised and 

 separated by a prominent intercondylar ridge. The outer edge of the distal surface 

 shows a narrow facet for the fibula, indicating that the latter had commenced to shift 

 beneath the tibia; though the narrowness of this facet and the large rugose surface 

 upon the external side of the tibia, make it probable that the redaction of the fibula 

 was by no means complete. It has, however, clearly begun. 



The foot structure of Leptotragulus is very curious, though we arc unfortunately 

 not in a position to give a complete account of it. The manus seems to have pos- 

 sessed four functional digits, and is represented in the specimen before us by the 

 proximal ends of what appear to be the second and fourth metacarpals. Mc. ii (?) 

 is slender, but hardly more reduced than in Oreodon. Its proximal end shows three 

 facets, of which the largest is a concave one for the trapezoid, and behind this a 

 separate one for the trapezium ; a small oblique sui-face towards the ulnar side seems 

 to be for the magnum, thus indicating an " unreduced '' type of manus. Mc. iv is 

 much stouter and has a trihedral shaft and a simple, saddle-shaped surface for the 

 unciform. On the ulnar side is a deep depression, apparently for the fifth metacarpal. 

 This account is given with reserve, as the fragments described are too imperfect for 

 certain identification, and the differences indicated between the fore and hind foot are 

 vei'y remarkable. 



The pes is fortunately much better preserved than the manus. The calcaneum 

 is rather long, compressed and deep, with approximately parallel edges. The fibular 

 facet is prominent, strongly arched from befoi-e backwards and descending abrujjtly 

 in front. An astragalar surface is on the inner side of this facet and forms a shai-p 

 angle with it. The distal end of the calcaneum is very narrow, but of considerable 

 antero-2:)Osterior extent, and bears upon its inner side an unusually large surface for 

 the astragalus. The latter is strikingly high and narrow ; the proximal condyles are 

 small and quite widely separated ; the outer one is divided by a considerable interval 

 from the cuboidal facet, while the innei' extends further down and reaches the navicu- 

 lar surface. The fibular facet upon the outer condyle is very long. The distal trochlea 

 is unevenly divided between the facets for the navicular and cuboid, the latter being 

 very narrow. The inferior surface foi" the susteatnctdicm tali is long and narrow and 

 separated by a deep pit from the overhanging external proximal condyle. The cuboid 

 is high, narrow, and deep (antero-posteriorly) ; the calcaneal facet is arched from 

 before backwards and in front descends much below that for the astragalus; it is also 

 slightly broader than the latter; upon the tibial side of the cuboid are two small 

 and widely separated facets for the navicular, the position of which indicates that the 



