The _calcaneum_ (Plate IX., Fig. 4) is long and compressed, with its upper and lower margins straight and nearly parallel; its tuberosity is large. The face for the cuboid is small. The _navicular_ (Plate IX., Fig. 6) is proportionately longer and narrower than it is in the modern horse. The internal and middle cuneiforms were probably separate. _Metatarsals_ (Plate IX., Fig. 7).--Three in number. Are very much shorter proportionately than in the modern horse. In shape they are compressed and arched forward. The distal ends are flattened vertically, arched forward, and deeply grooved in the middle. The _phalanges_ (Plate IX., Fig. 7) are very short, rather stout, and very smooth and convex above. The ungual phalanges are very thin and crescent shaped. _Measurements._ ASTRAGALUS. M. Greatest width ·029 Greatest length ·022 Length of navicular facet ·017 Width of navicular facet ·012 Length of tibial trochleæ externally ·016 CALCANEUM. M. Total length ·058 Total width ·019 Depth in front ·022 Length of heel ·035 Depth of heel ·018 Length of cuboid facet ·014 NAVICULAR. M. Width ·009 Length ·010 PHALANGES. M. Length of first phalanx ·022 Width of first phalanx ·012 Length of second phalanx ·013 Width of second phalanx ·010 Length of ungual phalanx ·005 Width of ungual phalanx ·010 PALÆOSYOPS, Leidy. Hayden's Geological Survey of Montana, 1871.--Proceedings Academy Natural Sciences, Philadelphia, 1871, p. 118.--_Limnohyus._--Marsh, American Journal Science and Arts, 1872, p. 124. _Generic characters._--The dentition is full, I. 3, C. 1, Pm. 4, M. 3; the same in lower jaw. The internal cones of the superior molars isolated from the crescentoid crests. One inner tubercle on the last three premolars. One internal cone on the last superior molar. In lower jaw, true molars with four acute tubercles alternating in pairs and connected by oblique crests. The last molar adds a fifth posterior tubercle. The last premolar lacks the posterior inner tubercle. The canines are in continuity with the incisors. A broad, triangular forehead. A wide zygoma. Long, projecting nasals. Large temporal fossæ. High sagittal crest. Prominent and nearly vertical occiput. Palæosyops major, Leidy.