CHAPTER XXVII. 
Ungulates, —cone luded. 
Hyraces, Elephants, etc. 
With the exception of the extinct phenacodus, noticed among the ancestors of 
the horse, the whole of the Ungulates described in the seven preceding chapters are 
characterised by certain peculiarities in the structure of the wrist-joint. On 
referring to the figure of the fore-foot of the titanothere on p. 152, it will be seen 
that the bones of the two rows of the wrist are arranged alternately to one 
another, that is to say, the bone marked l is placed immediately over the line of 
division between the bones u and to. Moreover, none of these animals have more 
than four toes to any one foot; while in no case do they walk on the whole sole 
of the foot after the so-called plantigrade fashion. Then, again, the huckle-bone, 
or astragalus, in the ankle-joint, is always deeply grooved, as shown in the hind- 
foot of a deer represented on p. 154, and in that of a rhinoceros on p. 455. 
On the other hand, in most of the Ungulates remaining for consideration the 
component bones of the two rows of the wrist-joint, 
as shown in the accompanying figure of the fore-foot 
of an elephant, are placed directly one over the other, 
so that the line of division between the bones l and c 
is continuous with that between to and u, instead of 
being placed immediately above to. And it will be 
obvious that this type of structure is inferior from 
a mechanical point of view to that distinguishing 
the wrist-joint of the typical Ungulates. The existing 
and many of the extinct Ungulates described in this 
chapter frequently have five toes on each foot, and 
not less than four functional ones, with a rudiment 
of a fifth on the fore-foot. They may likewise walk 
partly or entirely in the plantigrade manner; while in the ankle-joint the upper 
surface of the huckle-bone is generally flat. In all respects, therefore, so far as 
foot-structure is concerned, these animals are less highly organised than the 
Ungulates of which we have hitherto treated. The sole living representatives of 
Ungulates with this generalised type of foot structure are the small hyraces, of 
which there are numerous kinds, and the two species of elephant. The latter are, 
however, the last survivors from a number of kindred animals; and there formerly 
existed several other groups of more or less nearly-allied Ungulates which are 
now totally extinct. Beyond the generalised structure of their feet, there is but 
THE BONES OF THE LEFT FORE-FOOT 
OF AN ELEPHANT (£ liat. size). 
—After Osborn. 
