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300 GEOGEAPHICAL ZOOLOGY. [part iv.
Turdidge, aud the Paridae, are the only other families that ap-
proach universality of distribution, and all these are want-
ing in one or more sub-regions. If, now, we divide the
globe into the New and the Old World, the former including
the whole American continent, the latter all the rest of the
earth, we find that the Old World possesses exclusively 23
families, the New World exclusively 14, of which 5 are common
to North and South America. But if we take the division
proposed by Professor Huxley—a northern world, comprising
our first four regions (from Nearctic to Oriental), and a southern
world comprising our last two regions (the Australian and
Neotropical)—we find that the northern division possesses only
5 families exclusively, and the southern division 13 exclusively,
of which not one is common to Australia and South America.
This plainly indicates that, as far as the Passeres are concerned,
the latter bipartite division is not so natural as the former.
Again, if we compare temperate with tropical families (not too
rigidly, but as regards their general character), we find in the
northern hemisphere only two families that have the character
of being typically temperate—the Cinclidse, and in a less degree
the Ampelidse—both of small extent. In the southern hemi-
spliere we have also two, the Phytotomidse, and in a less degree,
the Pteroptochidse ; making two wholly and two mainly tem-
perate families. Of exclusively tropical families on the other
hand, we have about 12, and several others that are mainly
tropical.
The several regions do not differ greatly in the number of
families found in each. The Nearctic has 19, the Palsearctic 21,
the Ethiopian 23, the Oriental 28, the Australian 29, and the
Neotropical 23. But many of these families are only represented
by a few species, or in limited districts ; and if we count only those
families which are tolerably well represented, and help to form
the ornithological character of the region, the richness of the
several tropical regions wUl appear to be (as it really is) com-
paratively much greater. The families that are confined to
single regions are not very numerous, except in the case of
the Neotropical region, which has 5. The Australian has only