U 2 
UNGULATES. 
In all the Ungulates the limbs have entirely ceased to be used as organs of 
prehension, and there would seem to be no necessity why there should be any 
adherence to the primitive five-toed type, as development advances. The majority 
of the members of the order being, however, unable to protect themselves against 
foes, and being also, in proportion to their height, heavy-bodied animals, the attain¬ 
ment of a high degree of speed was essential to their well-being and development, 
if not for their actual existence. For such a kind of life it will be obvious that 
the greater the length and slenderness of limb, the greater will at first sight be the 
speed. Now, in order to produce a long and slender, and at the same time a strong 
limb, from a stout and short-toed one, greater strength will clearly be attained by 
reducing the number of the toes, and lengthening and strengthening those which 
remain, rather than by lengthening the whole of the five 
toes, the slender bones of which would be liable to fracture 
by the concussion of the solid hoofs against the ground. 
Accordingly, among the Ungulates, the plan has been to 
gradually lengthen and strengthen the bones of one or more 
of the original five toes, and at the same time to dispense 
more or less completely with the others. In almost the 
lowest Tertiary rocks of Europe and North America there 
occur, for instance, the remains of certain large Ungulates, 
known as coryphodons, in which both the fore and hind-feet 
(as represented in the accompanying figure) have five com¬ 
plete toes. It will be observed that both the metacarpal 
bones and the toe bones by which they are succeeded are very 
short; and these animals must accordingly have walked to a 
certain extent upon the soles of their feet in the old-fashioned 
plantigrade manner . 1 It will also be noticed that the third 
or middle toe (in) is larger than either of the others, and symmetrical in itself. 
Another feature of this type of foot is that the component bones forming the two 
horizontal rows of the wrist are placed almost verti¬ 
cally one above another, the bone lettered l merely 
touching the adjacent angle of the one marked u. 
When we ascend to the overlying Miocene 
Tertiary deposits we meet with other large 
Ungulates having a foot of the type of that 
shown in our second figure, where it will be 
noticed that while all trace of the first toe (i) has 
disappeared, the metacarpal bones of all the others 
have become very much more elongated, in con¬ 
sequence of which the animal no longer walked 
upon the soles of its feet, but entirely upon the 
toes, or was, in other words, digitigrade. It will 
also be observed that the third toe has become 
still larger in proportion to the others. Moreover, the upper row of wrist-bones 
BONES OF THE LEFT WRIST 
AND FORE-FOOT OF THE 
cortphodon (j nat. size). 
The letters indicate the 
bones of the wrist (cuneiform, 
lunar scaphoid, trapezium, 
trapezoid, magnum, unciform), 
and the numerals those of the 
metacarpus.—After Osborn. 
bones of the left wrist and foot of 
the titanothere nat. size).—After 
Osborn. 
1 As a matter of fact, the coryphodon was partially digitigrade in its fore-feet, but entirely plantigrade in the 
hinder ones. 
