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CHAP. XIV.] THE NEOTROPICAL REGION. 25
15 in peculiar types of all the most characteristic American
families, such as the Tanagridse, Tyrannidae, Cotingidse, Formi-
cariidse, Trochilidse, and Galbulidse. A considerable proportion
of the genera of the Chilian aad Mexican sub-regions also
occur here, so that out of about 680 genera of Neotropical land-
birds more than 500 are represented in this sub-region.
Without entering minutely into the distribution of species it
is difficult to sub-divide this extensive territory with any satis-
factory result.^ The upland tract between the Amazon and
Orinooko, which may be termed Guiana, was evidently once an
island, yet it possesses few marked distinctive features. Brazil,
which must have formed another great island, has more speciality,
but the intermediate Amazonian forests form a perfect transition
between them. The northern portion of the continent west of
the Orinooko has more character ; and there are indications that
this has received many forms from Central and North America,
and thus blended two faunas once more distinct than they are
now. The family of wood-warblers (Mniotiltidee) seems to have
belonged to this more northern fauna ; for out of 18 genera only
5 extend south of the equator, while 6 range from Mexico or
the Antilles into Columbia, some of these being only winter
immigrants and pp genus being exclusively South American.
The eastern slopes of the Andes constitute, however, the richest
and best marked province of this sub-region. At least 12 genera
of tanagers (Tanagridae) are found here only, with an immense
number of Fringillidae,—the former confined to the forests, the
latter ranging to the upland plains. The ant-thrushes (Formi-
cariidse) on the other hand seem more abundant in the lowlands,
many genera being peculiar to the Amazonian forests. The su-
perb chatterers (Cotingidse) also seem to have their head-quarters
in the forests of Brazil and Guiana, and to have thence spread
^ Messrs. Sclater and Salvin, and Professor Newton, divide the Neotropical
Region into six sub-regions, of which our " Brazilian sub-region " comprises
three—the " Brazilian," the " Amazonian," and the " Columbian ; " but,
after due consideration, it does not seem advisable to adopt this subdivision
in a general work which treats of aU the classes of terrestrial animals. (See
p. 27.)