era of the Iguanidae, a family which is exclusively
American; while a genus of geckoes, inhabiting America and Australia, also
occurs in Madagascar.

_Relation of Madagascar to Africa._--These facts taken all together are
certainly very extraordinary, since they show in a considerable number of
cases as much affinity with America as with Africa; while the most striking
and characteristic groups of animals now inhabiting Africa are entirely
wanting in Madagascar. Let us first deal with this fact, of the absence of
so many of the most dominant African groups. The explanation of this
deficiency is by no means difficult, for the rich deposits of fossil
mammals of Miocene or Pliocene age in France, Germany, Greece, and
North-west India, have demonstrated the fact that all the great African
mammals then inhabited Europe and temperate Asia. We also know that a
little earlier (in Eocene times) tropical Africa was cut off from Europe
and Asia by a sea stretching from the Atlantic to the Bay of Bengal, at
which time Africa must have formed a detached island-continent such as
Australia is now, and probably, like it, very poor in the higher forms of
life. Coupling these two facts, the inference seems clear, that all the
higher types of mammalia were developed in the great Euro-Asiatic continent
(which then included Northern Africa), and that they only migrated into
tropical Africa when the two continents became united by the upheaval of
the sea-bottom, probably {419} in the latter portion of the Miocene or
early in the Pliocene period.[99]

It is clear, therefore, that if Madagascar had once formed part of Africa,
but had been separated from it before Africa was united to Europe and Asia,
it would not contain any of those kinds of animals which then first entered
the country. But, besides the African mammals, we know that some birds now
confined to Africa then inhabited Europe, and we may therefore fairly
assume that all the more important groups of birds, reptiles, and insects,
now abundant in Africa but absent from Madagascar, formed no part of the
original African fauna, but entered the country only after it was joined to
Europe and Asia.

_Early History of Africa and Madagascar._--We have seen that Madagascar
contains an abundance of mammals, and that most of them are of types either
peculiar to, or existing also in, Africa; it follows that that continent
must have had an earlier union with Europe, Asia, or America, or it coul