334 SCOTT. [Vol. V. 



is no connection with the median digit. The ectocuneiform is 

 high and narrow proportionately; its proximal and distal sur- 

 faces are D-shaped, with the curve directed anteriorly, and a 

 short, narrow tongue directed posteriorly from the hinder edge. 

 The navicular surface is emarginated by a small fossa on the 

 fibular edge ; the distal facet also shows a very shallow oval 

 fossa, but the articular surface of the tongue, or posterior pro- 

 longation, is continuous with that of the body of the bone, nor 

 is its free end transversely extended. There is a small and 

 sessile antero-inferior facet for the cuboid, and a larger postero- 

 superior one. There is also on the tibial side of the posterior 

 prolongation a small facet for the second metatarsal. 



In AnchitJierium, the ecto- and mesocuneiforms are co-ossified, 

 and the entocuneiform is free. The former is broader and 

 lower than in the American genus, and of very different shape, 

 as is especially shown in the fact that the posterior tongue or 

 beak is directed toward the fibular side, instead of backward 

 (cf. PL XXIII., Fig. 36, with Kowalevsky/PL II., Fig. 23). 

 There is on this beak no facet for the second metatarsal. 



In the horse, the ento- and mesocuneiforms are co-ossified, as 

 in Mesohippus, though in some specimens all three of the bones 

 are distinct, and Forsyth Major states that, as a rare exception, 

 the ecto- and mesocuneiforms unite (No. 18, p. 62). The ecto- 

 cuneiform is greatly increased in breadth and is very low ; the 

 beak is very much wider, and bears at its posterior end a 

 distinct broad facet for metatarsal III., which is separated by 

 a wide fossa from the anterior one ; the latter is reduced in 

 antero-posterior extent, as compared with that of Mesohippus. 

 There is normally no facet on cu. 3 for the second metatarsal ; 

 but Kowalevsky reports finding it rarely, and then associated 

 with a reduction in width of the facet for metatarsal III. upon 

 the beak (No 25, p. 45). The mesocuneiform presents two 

 distal facets, for the second and third metatarsals respectively. 

 As a whole, the tarsus of Equus, compared with that of Meso- 

 hippus, has decreased in height and increased in breadth and 

 depth, and is especially modified by the connection of the 

 median metatarsal with all three of the distal tarsal elements. 



The metatarsus of Mesohippus (PL XXIII., Fig. 39) consists 

 of the second, third, and fourth metatarsals, the fifth having 

 completely disappeared. Metatarsal II. is very much compressed 



