ion of the northern,
eastern, and south-western coasts. We may therefore conclude that during
Tertiary times the island was usually as large as, and often probably much
larger than, it is now. {415}

[Illustration: MAP OF THE MADAGASCAR GROUP, SHOWING DEPTHS OF SEA.]

In this Map the depth of the sea is shown by three tints; the lightest tint
indicating from 0 to 100 fathoms, the medium tint from 100 to 1,000
fathoms, the dark tint more than 1,000 fathoms.

{416}

_Biological Features of Madagascar._--Madagascar possesses an exceedingly
rich and beautiful fauna and flora, rivalling in some groups most tropical
countries of equal extent, and even when poor in species, of surpassing
interest from the singularity, the isolation, or the beauty of its forms of
life. In order to exhibit the full peculiarity of its natural history and
the nature of the problems it offers to the biological student, we must
give an outline of its more important animal forms in systematic order.

_Mammalia._--Madagascar possesses no less than sixty-six species of
mammals--a certain proof in itself that the island has once formed part of
a continent; but the character of these animals is very extraordinary and
altogether different from the assemblage now found in Africa or in any
other existing continent. Africa is now most prominently characterised by
its monkeys, apes, and baboons; by its lions, leopards, and hyaenas; by its
zebras, rhinoceroses, elephants, buffaloes, giraffes, and numerous species
of antelopes. But no one of these animals, nor any thing like them, is
found in Madagascar, and thus our first impression would be that it could
never have been united with the African continent. But, as the tigers, the
bears, the tapirs, the deer, and the numerous squirrels of Asia are equally
absent, there seems no probability of its having been united with that
continent. Let us then see to what groups the mammalia of Madagascar
belong, and where we must look for their probable allies.

First and most important are the lemurs, consisting of six genera and
thirty-three species, thus comprising just half the entire mammalian
population of the island. This group of lowly-organised and very ancient
creatures {417} still exists scattered over a wide area; but they are
nowhere so abundant as in the island of Madagascar. They are found from
West Africa to India, Ceylon, and the Malay Archipelago, consisting of a
number of isolated genera and species,