the very small amount of depression the land need have
undergone to produce it.

But the fact of the Aru Islands having once been connected with New
Guinea does not rest on this evidence alone. There is such a striking
resemblance between the productions of the two countries as only exists
between portions of a common territory. I collected one hundred species
of land-birds in the Aru Islands, and about eighty of them, have been
found on the mainland of New Guinea. Among these are the great wingless
cassowary, two species of heavy brush turkeys, and two of short winged
thrushes; which could certainly not have passed over the 150 miles of
open sea to the coast of New Guinea. This barrier is equally effectual
in the case of many other birds which live only in the depths of the
forest, as the kinghunters (Dacelo gaudichaudi), the fly-catching wrens
(Todopsis), the great crown pigeon (Goura coronata), and the small wood
doves (Ptilonopus perlatus, P. aurantiifrons, and P. coronulatus).
Now, to show the real effect of such barrier, let us take the island of
Ceram, which is exactly the same distance from New Guinea, but separated
from it by a deep sea. Cut of about seventy land-birds inhabiting Ceram,
only fifteen are found in New Guinea, and none of these are terrestrial
or forest-haunting species. The cassowary is distinct; the kingfishers,
parrots, pigeons, flycatchers, honeysuckers, thrushes, and cuckoos, are
almost always quite distinct species. More than this, at least twenty
genera, which are common to New Guinea and Aru, do not extend into
Ceram, indicating with a force which every naturalist will appreciate,
that the two latter countries have received their faunas in a radically
different manner. Again, a true kangaroo is found in Aru, and the same
species occurs in Mysol, which is equally Papuan in its productions,
while either the same, or one closely allied to it, inhabits New Guinea;
but no such animal is found in Ceram, which is only sixty miles from
Mysol. Another small marsupial animal (Perameles doreyanus) is common
to Aru and New Guinea. The insects show exactly the same results. The
butterflies of Aru are all either New Guinea species, or very slightly
modified forms; whereas those of Ceram are more distinct than are the
birds of the two countries.

It is now generally admitted that we may safely reason on such facts
as those, which supply a link in the defective geological record. The
upward and downward