332 SCOTT. [Vol. V. 



an inferior one for the ectocuneiform. The distal surface is 

 much smaller than the proximal and bears a slightly convex, 

 rounded facet for the fourth metatarsal ; on the tibial side there 

 is a very small, entirely lateral facet for the third metatarsal, 

 which is enabled to touch the cuboid laterally, because the latter 

 projects below the ectocuneiform, having a height greater than 

 that bone and the navicular combined. 



In the cuboid of AnchitJierium the calcaneal facet is more 

 distinctly divided into anterior and posterior portions, the latter 

 being very much narrower and somewhat recurved. The facet 

 for metatarsal III. is of very different shape, being broader in 

 front and narrower behind, and that for metatarsal IV. is more 

 oblique in position, presenting downward as well as inward. 

 The whole bone is more massive and thickened, and the poste- 

 rior projection longer and more rugose. 



In the horse, the cuboid has become very different. The 

 calcaneal facet is now very distinctly divided into anterior and 

 posterior portions, though the two are still continuous, and the 

 latter is strongly incurved. There is a large antero-superior 

 facet for the navicular, the astragalus no longer intervening be- 

 tween the two ; the posterior facet for the navicular and ectocu- 

 neiform is much more prominent than in Mesohippus. The 

 distal surface also exhibits important changes. The facet for 

 metatarsal III. is very much larger and altogether distal in 

 position, while that for metatarsal IV. has become very oblique 

 and rather more lateral than distal ; an additional facet for this 

 metatarsal appears on the postero-internal angle. The cuboid 

 does not descend below the ectocuneiform. 



The navicular of MesoJiippus is low and broad, though rela- 

 tively higher and narrower than in the existing genus. The 

 proximal surface is concave and the posterior margin consider- 

 ably elevated at its inner and outer angles ; between the two is 

 the wide depression for the corresponding process from the 

 astragalus. There is a small triangular space in the navicular 

 facet, which extends toward, but does not reach, the fibular 

 margin ; this represents the fossa which occurs in the horse and 

 is more clearly shown than the corresponding structure on the 

 astragalus. There is no anterior facet for the cuboid : when 

 the two bones are placed in position, they divaricate anteriorly ; 

 the posterior cuboidal facet is quite large and is continuous 



