tions of convenience, dependent on custom and on the more or less perfect knowledge we possess of some of the intervening countries.

Zoological Characteristics of the Palearctic Region.-The Palæarctic region has representatives of thirty-five families of mammalia, fifty-five of birds, twenty-five of reptiles, nine of amphibia, and thirteen of freshwater fishes. Comparing it with the only other wholly temperate region, the Nearctic, we find a much greater variety of types of mammalia and birds. This may be due in part to its greater area, but more, probably, to its southern boundary being conterminous for an enormous distance with two tropical regions, the Ethiopean and Oriental; whereas the Nearctic has a comparatively short southern boundary conterminous with the Neotropical region only. This is so very important a difference, that it is rather a matter of surprise that the two north temperate regions should not be more unequal in the number of their higher vertebrate forms, than they actually are.

It is also to the interblending of the Palearctic with the two adjacent tropical regions, that we must attribute its possession of so few peculiar family groups. These are only three; two of reptiles, Trogonophido and Ophiomoride, and one of fishes, Comephorida. The number of peculiar genera is, however, considerable, as the following enumeration will show.

Mammalia.-The monkey of Gibraltar and North Africa, and an allied species found in Japan, are now considered to belong to the extensive eastern genus Macacus. The former, however, is peculiar in the entire absence of the tail, and has by many naturalists, been held to form a distinct genus, Inuus, confined to the Palearctic region.

Of bats there are one or two genera (Barbastellus, Plecotus) which seem to be mainly or wholly Palearctic, but the classification of these animals is in such an unsettled state that the distribution of the genera is of little importance.

In the next order, Insectivora, we have almost the entire family of the Moles confined to the region. Talpa just enters Northern India; and Urotrichus is common to Japan and North