land connection
with the nearest continental area was very remote in time. The
extraordinary isolation of the productions of Madagascar--almost all the
most characteristic forms of mammalia, birds, and reptiles of Africa
being absent from it--renders it certain that it must have been
separated from that continent very early in the Tertiary, if not as far
back as the latter part of the Secondary period; and this extreme
antiquity is indicated by a depth of considerably more than a thousand
fathoms in the Mozambique Channel, though this deep portion is less than
a hundred miles wide between the Comoro Islands and the mainland.[166]
Madagascar is the only island on the globe with a fairly rich mammalian
fauna which is separated from a continent by a depth greater than a
thousand fathoms; and no other island presents so many peculiarities in
these animals, or has preserved so many lowly organised and archaic
forms. The exceptional character of its productions agrees exactly with
its exceptional isolation by means of a very deep arm of the sea.

New Zealand possesses no known mammals and only a single species of
batrachian; but its geological structure is perfectly continental. There
is also much evidence that it does possess one mammal, although no
specimens have been yet obtained.[167] Its reptiles and birds are highly
peculiar and more numerous than in any truly oceanic island. Now the sea
which directly separates New Zealand from Australia is more than 2000
fathoms deep, but in a north-west direction there is an extensive bank
under 1000 fathoms, extending to and including Lord Howe's Island, while
north of this are other banks of the same depth, approaching towards a
submarine extension of Queensland on the one hand, and New Caledonia on
the other, and altogether suggestive of a land union with Australia at
some very remote period. Now the peculiar relations of the New Zealand
fauna and flora with those of Australia and of the tropical Pacific
Islands to the northward indicate such a connection, probably during the
Cretaceous period; and here, again, we have the exceptional depth of the
dividing sea and the form of the ocean bottom according well with the
altogether exceptional isolation of New Zealand, an isolation which has
been held by some naturalists to be great enough to justify its claim to
be one of the primary Zoological Regions.

_The Teachings of the Thousand-Fathom Line._

If now we accept the annexed ma