all but the bovines and their near allies, and are thus far advanced
toward our definition of a bison, but from this point we shall not find
it easy to draw sharp distinctions, for while the _Bovidae_, as a
whole, are well enough distinguished from all other animals, their
characteristics are so much mixed among themselves that it is hardly
possible to find any one or more striking features peculiar to one
group, and for most of them recourse must be had to associations of a
number of lesser characters.

Oxen, antelopes, sheep and goats agree in having hollow horns of
material similar to that of which hair and nails are formed, permanently
fixed upon the skull in all but one species; none of them have more than
the two middle digits functionally developed, one on each side of the
axis of the leg; none have the lower ends remaining of the meta-podial
bones belonging to the two accessory digits; and none have either
incisor or canine teeth in the upper jaw.

From animals so constructed we may first take out goats and sheep, in
which the female horns are much smaller than those of males, and in some
species are even absent. In nearly all of them the horns are noticeably
compressed in section, either triangular or sub-triangular near the
base, and are directed sometimes outwardly from the head with a circular
sweep; at others with a backward curve, often spirally. The muzzle is
always hairy; there is no small accessory column on the inner side of
the upper molars, found always in oxen and in some antelopes; the tail
is short, and scent glands are present between the digits of some or all
the feet.

Now, as to the perplexing animals popularly known as antelopes. No
definition could be framed which would include them all in one group,