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CHAP, xviii.] BIRDS. 301
3, the Oriental 1, the Ethiopian 1, and the other regions have
no peculiar families.
The distribution of the Passeres may be advantageously
considered as divided into the five series of Turdoid, Tanagroid,
Sturnoid, Formicarioid, and Anomalous Passeres. The Turdoid
Passeres, consisting of the first 23 families, are especially
characteristic of the Old World, none being found exclusively
in America, and only two or three being at all abundant there.
The Tanagroid Passeres (Families 24-33) are very characteristic
of the New World, five being confined to it, and three others
being quite as abundant there as in the Old World ; while there
is not a single exclusively Old World family in the series,
except the Drepanididse confined to the Sandwich Islands.
The Sturnoid Passeres (Families 34-38) are all exclusively Old
World, except that two larks inhabit parts of North America,
and a few pipits South America. The Formicarioid Passeres
(Families 39-48) are strikingly characteristic of the New World,
to which seven of the families exclusively belong; the two
Old World groups being small, and with a very restricted
distribution. The Anomalous Passeres (Families 49-50) are
confined to Australia.
The most remarkable feature in the geographical distribution
of the Passeres is the richness of the American continent, and
the large development of characteristic types that occurs there.
The fact that America possesses 14 altogether peculiar families,
while no less than 23 Old-World families are entirely absent from
it, plainly indicates, that, if this division does not represent the
most ancient and radical separation of the land surface of the
globe, it must still be one of very great antiquity, and have
modified in a very marked way the distribution of all living
things. Not less remarkable is the richness in specific forms
of the 13 peculiar American families. These contain no less
than 1,570 species, leaving only about 500 American species in
the 13 other Passerine families represented in the New World.
If we make a deduction for those Nearctic species which occur
only north of Panama, we may estimate the truly Neotropical
species of Passerine birds at 1,900, which is almost exactly