No. 3.] OSTEOLOGY OF MESOHIPPUS AND LEPTOMERYX. 335 



laterally, and has a long, very slender shaft. The head is ex- 

 panded antero-posteriorly and bears two facets, one proximal for 

 the mesocuneiform, the other oblique and posterior for the ento- 

 cuneiform : there is also a small lateral facet for the tongue of 

 the ectocuneiform, but there appears to be no anterior contact 

 with the latter in some specimens, though there clearly is in 

 others. Connection with the median metatarsal is by means of 

 ill-defined facets. The distal end is much compressed and 

 slightly recurved, with a sharp keel on the plantar side of the 

 trochlea ; the portion of the trochlea medial to the keel is 

 decidedly more prominent than the external portion. 



The third metatarsal is very long and slender ; proximally it 

 is narrow and deep, distally it becomes broader and flattened 

 antero-posteriorly. The head bears a facet for the ectocunei- 

 form, which is broad, with a rounded anterior margin and a 

 narrow posterior tongue or beak. The articular surface is con- 

 tinuous over the proximal end, being only slightly interrupted 

 by a small fossa. The facet for the cuboid is small and some- 

 what oblique, but more lateral than proximal in position. There 

 are two small facets for the fourth metatarsal, which are placed 

 very near together. The distal end of the shaft is quite broad 

 and has two lateral tubercles for ligamentous attachments ; the 

 trochlea is narrower and is terminated above by a deep pit. 

 The carina is more prominent than on the median metacarpal, 

 and there is a very obscure indication of it upon the anterior 

 face. The proportions of this digit vary considerably in the 

 different specimens, being decidedly stouter in some than in 

 others. 



The second metatarsal rises higher than the third, and the 

 third higher than the fourth. The latter is slightly stouter 

 than the second and has a more thickened and rugose head ; 

 it bears a single facet for the cuboid, but there is in some indi- 

 viduals a posterior prolongation of this, which may be regarded 

 as the beginning of a second one. 



In the metatarsus of Anchitherinm the median digit is de- 

 cidedly larger proportionately than in the American form, and 

 in particular the head is transversely extended ; its articulations 

 are also different, in that the cuboidal facet shows a stronger 

 tendency to become proximal, and a small connection with the 

 mesocuneiform is established. Distally the shaft is still broader 



