The number of distinct species of sheep in our fauna is a matter of too
much uncertainty to be treated with any sort of authority at this time.
Most of us grew up in the belief that there was but one, the well-known
mountain sheep (_Ovis canadensis_), but seven new species and
sub-species have been produced from the systematic mill within recent
years, six of them since 1897. It is no part of the purpose of the
present paper to dwell upon much vexed questions of specific
distinctness, and it will only be pointed out here that the ultimate
validity of most of these supposed forms will depend chiefly upon the
exactness of the conception of species which will replace among
zoologists the vague ideas of the present time. Whatever the conclusion
may be, it seems probable that some degree of distinction will be
accorded to, at least, one or two Alaskan forms.

As sheep probably came into America from Asia during the Pleistocene, at
a time when Bering's Strait was closed by land, it might be expected
that those now found here would show relationship to the Kamtschatkan
species (_Ovis nivicola_); and such is indeed the case, while
furthermore, in the small size of the suborbital gland and pit, and in
comparative smoothness of the horns, both species approach the bharal of
Thibet and India, which in these respects is goat-like.

When one considers the poverty of the new world in bovine ruminants, it
seems strange that three such anomalous forms should have fallen to its
share as the prong-horn, the white goat and the musk-ox, of none of
which have we the complete history; two of the number being entirely
isolated species, sometimes regarded as the types of separate families.

The prong-horn is a curious compound. It resembles sheep in the minute