314 THE OSTEOLOGY OF ELOTHERIUM. 
1, tens, 12g. 
The tarsus has undergone little specialization, although the hind foot, like the fore 
foot, is didactyl. 
The astragalus is elongate, though broad and massive as well. The proximal 
trochlea is deeply but very broadly grooved and its two parts are unequal, the external 
condyle rising much more, both proximally and dorsally, than the internal, but not pro- 
duced so far distally. While the outer condyle is widely separated from the cuboidal 
facet, the inner one is continued so far distally as to become confluent with the nayicular 
surface. A very large and deep pit occupies a great part of the dorsal surface between 
the proximal and distal trochlez. The distal trochlea is broad and is unequally diyided 
into facets for the cuboid and navicular, the latter being much the wider and of a different 
shape. The surface for the cuboid is strongly convex in the dorso-plantar direction, but 
nearly plane transyersely, while the navicular facet is hour-glass shaped, and on the fibular 
side of the median line has a distinct, though wide and shallow groove for a corresponding 
ridge on the proximal side of the nayicular. The junction of the two facets forms a sharp 
but not prominent edge. 
The facets for the caleaneum somewhat resemble those which we find in Ancodus, 
but they have not attained to such a degree of specialization as in the American species of 
that genus. The proximal external facet is divided by a sulcus into two parts, both of 
which are concaye and present distally, as well as laterally. The proximal portion is set 
on a conspicuous prominence of the fibular side of the astragalus, and is clearly visible 
when the bone is seen from the dorsal side, while the distal portion is also prominent, but 
is concealed when looked at from the same point of yiew. ‘The sustentacular facet is very 
large and is strongly conyex in the proximo-distal direction, but almost plane trans- 
versely ; its external border projects as a shelf beyond the body of the astragalus, and 
thus helps to enclose the large and deep sulcus which is found upon the external side of 
the bone. The distal external facet for the calcaneum is very small. The fibular facet 
is well extended in the proximo-distal diameter, but is narrow in the dorso-plantar 
direction. 
In Kowalevsky’s specimen (’76, Taf. X XVII, Fig. 34) the astragalus, so far as it is 
preserved, resembles that of the American species, but the external part of the proximal 
trochlea is too much damaged to show the characteristic external calcaneal facet. In 
Anthracotherium (Kowaleysky, °75, Taf. XI, Fig. 59, de Blainyille, Ostéographie, 
Anthraco., Pl. IL) the astragalus is proportionately much broader and lower than in 
Elotherium, the ridge on the distal trochlea, formed by the junction of the two facets, is 
more prominent and pursues a more oblique course. The sustentacular facet is narrower 
and shorter and the proximal calcaneal facet projects less. The astragalus of Sus is quite 
