THE MAMMALIA OF THE DEEP RIVER BEDS. 8L 



does not occur in the specimen, but in all probability this is an individual, or, at 

 most, a species character. 



The navicular is a little lower relatively, and has also increased in transverse 

 breadth, more particularly towards the internal or tibial side. The posterior margin 

 of the astragalar surface is less elevated and less widely notched, and the posterior 

 projection which extends towards the cuboid is less prominent. As in the case of 

 the astragalus, the corresponding sulcus is absent. On the distal side, the facet for 

 the ectocuneiform has increased in size, and that for the combined meso- and ento- 

 cunei forms has become somewhat more posterior in position. The anterior face of 

 the navicular is decidedly less curved. 



The cuboid has slightly increased its dorso-plantar diameter and the posterior 

 hook has become decidedly more massive and rugose, even more so relatively than in 

 JEquus. The astragalar surface is wider, and the hinder part of the calcaneal facet 

 broader, more incurved and more equine in shape. 



The ectocuneiform is broader and lower, but otherwise as in Mesohippus. Al- 

 though the animal was fully adult, the suture between the ento- and meso cuneiforms 

 is very clearly shown, much more so than in any White Eiver specimen which has 

 come under my observation, and the ankylosis of the two elements appears to be a 

 somewhat loose one. This, again, is doubtless an individual character. The euto- 

 cuneiform in both genera extends across to a contact with the cuboid, though in 

 Miohippus it is relatively larger, especially in vertical diameter. The navicular facet 

 on the mesocuneiform is somewhat more concave and rises higher behind. 



In the metatarsals, the only noteworthy change is in the increase in size of the 

 median one, though its articulations remain as before ; it is still excluded from con- 

 tact with the mesocuneiform by the junction of the second metatarsal with the ecto- 

 cuneiform, which is very limited. 



Measurements. m. 



Length of femur • 325 



Width of distal end (transverse) • ° 47 



Depth of distal end (fore and aft) 057 



Length of tibia 363 



Width of proximal end 050 



Depth of proximal end 048 



Width of distal end (including fibula) °37 



Depth of distal end at inner astragalar groove 026 



Length of calcaneum 068 



Length of astragalus 032 



Width of astragalus head 022 



Width of proximal end of third metatarsal • • 020 



Depth of proximal end of third metatarsal 016 



