These fishes, however, probably pass part of their lives in the sea.
We thus certainly have several species which _are_ common to the fresh waters of distant continents, although it cannot be certainly affirmed that they are exclusively and entirely fresh-water fishes throughout all their lives except in the case of _Galaxias_.
Existing forms point to a close union between South America and Africa on the one hand, and between South America, Australia, Tasmania, and New Zealand on the other; but these unions were not synchronous any more than the unions indicated between India and Australia, China and Australia, China and North America, and India and Africa.
Pleurodont lizards are such as have the teeth attached by their sides {148} to the inner surface of the jaw, in contradistinction to acrodont lizards, which have the bases of their teeth anchylosed to the summit of the margin of the jaw.

Now pleurodont iguanian lizards abound in the South American region; but nowhere else, and are not as yet known to inhabit any part of the present continent of Africa.

Yet pleurodont lizards, strange to say, are found in Madagascar.

This is the more remarkable, inasmuch as we have no evidence yet of the existence in Madagascar of fresh-water fishes common to Africa and South America.
[Illustration: INNER SIDE OF LOWER JAW OF PLEURODONT LIZARD.
(Showing the teeth attached to the inner surface of its side.)] Again, that remarkable island Madagascar is the home of very singular and special insectivorous beasts of the genera Centetes, Ericulus, and Echinops; while the only other member of the group to which they belong is Solenodon, which is a resident in the West Indian Islands, Cuba and Hayti.
The connexion, however, between the West Indies and Madagascar must surely have been at a time when the great lemurine group was absent; for it is difficult to understand the spread of such a form as Solenodon, and at the same time the non-extension of the active lemurs, or their utter extirpation, in such a congenial locality as the West Indian Archipelago.
The close connexion of South America and Australia is demonstrated (on the Darwinian theory), not only from the marsupial fauna of both, but also from the frogs and toads which respectively inhabit those regions.

A truly remarkable similarity and parallelism exist, however, between certain of the same animals inhabiting South Western America and Europe.