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80 ZOOLOGICAL GEOGRAPHY. [part m.
conditions, of once wide-spread groups. If no wild species
of the genus Equus were now to be found, except in South
Africa (where they are still most abundant), and in South
Temperate America, where their fossil remains show us they did
exist not very long ago, what a strong fact it would have
Yet it
appeared for the advocates of continental extensions !
would have been due to no former union of the great southern
continents, but to the former extensive range of the family or
the genus to which the two isolated remnants belonged. And if
such an explanation will apply to the higher vertebrata, it is
still more likely to be applicable to similar cases occurring among
insects or moUusca, the genera of which we have every reason to
beheve to be usually much older than those of vertebrates. It
is. in these classes that examples of widely scattered allied
species most frequently occur ; and the facility with which they
are diffused under favourable conditions, renders any other
explanation than that here given altogether superfluous.
The Solenodon is a member of an order of Mammalia of low
type (Insectivora) once very extensive and wide-spread, but
which has begun to die out, and which has left a number of
curious and isolated forms thinly scattered over three-fourths of
the globe. The occurrence, therefore, of an isolated remnant of
this order in the Antilles is not in itself remarkable ; and the
fact that the remainder of the family to which the Antillean
species belong has found a refuge in Madagascar, where it has
developed into several distinct types, does not afford the least
shred of argument on which to found a supposed independent
land connection between these two sets of islands.
Summary of the Past History of the Neotropical Region.
"We have already discussed this subject, both in our account
of extinct animals, and in various parts of the present chapter.
It is therefore only necessary here, briefly to review and sum-
marise the conclusions we have arrived at.
The whole character of Neotropical zoology, whether as regards
its deficiencies or its speciahties, points to a long continuance
of isolation from the rest of the world, with a few very distant