r shaft intimately united with the radius,
is completely traceable. The fibula appears to be in the same condition
as in the horse. The teeth of the _Hipparion_ are essentially similar to
those of the horse, but the pattern of the grinders is in some respects
a little more complex, and there is a depression on the face of the
skull in front of the orbit, which is not seen in existing horses.

In the earlier Miocene, and perhaps the later Eocene deposits of some
parts of Europe, another extinct animal has been discovered, which
Cuvier, who first described some fragments of it, considered to be a
_Palaeotherium_. But as further discoveries threw new light on its
structure, it was recognized as a distinct genus under the name of
_Anchitherium_.

In its general characters, the skeleton of _Anchitherium_ is very
similar to that of the horse. In fact, Lartet and De Blainville called
it _Palaeotherium equinum_ or _hippoides_; and De Christol, in 1847, said
that it differed from _Hipparion_ in little more than the characters of
its teeth, and gave it the name of _Hipparitherium_. Each foot possesses
three complete toes; while the lateral toes are much larger in
proportion to the middle toe than in _Hipparion_, and doubtless rested
on the ground in ordinary locomotion.

The ulna is complete and quite distinct from that radius, though firmly
united with the latter. The fibula seems also to have been complete. Its
lower end, though intimately united with that of the tibia, is clearly
marked off from the latter bone.

There are forty-four teeth. The incisors have no strong pit. The canines
seem to have been well developed in both sexes. The first of the seven
grinders, which, as I have said, is frequently absent, and when it does
exist, is small in the horse, is a good-sized and permanent tooth,
while the grinder which follows it is but little larger than the hinder
ones. The crowns of the grinders are short, and though the fundamental
pattern of the horse-tooth is discernible, the front and back ridges are
less curved, the accessory pillars, are wanting, and the valleys, much
shallower, are not filled up with cement.

Seven years ago, when I happened to be looking critically into the
bearing of palaeontological facts upon the doctrine of evolution, it
appeared to me that the _Anchitherium_, the _Hipparion_, and the modern
horses, constitute a series in which the modifications of structure
coincide with the order of chronologi