ile in a recent paper by Dr. Steindachner, the marine species is again
classed as Amblyrhynchus, while the terrestrial form is placed in another
genus Conolophus, both genera being peculiar to the Galapagos.

How these lizards reached the islands we cannot tell. The fact that they
all belong to American genera or families indicates their derivation from
that continent, while their being all distinct species is a proof that
their arrival took place at a remote epoch, under conditions perhaps
somewhat different from any which now prevail. It is certain that animals
of this order have some means of crossing the sea not possessed by any
other land vertebrates, {280} since they are found in a considerable number
of islands which possess no mammals nor any other land reptiles; but what
those means are has not yet been positively ascertained.

It is unusual for oceanic islands to possess snakes, and it is therefore
somewhat of an anomaly that two species are found in the Galapagos. Both
are closely allied to South American forms, and one is hardly different
from a Chilian snake, so that they indicate a more recent origin than in
the case of the lizards. Snakes it is known can survive a long time at sea,
since a living boa-constrictor once reached the island of St. Vincent from
the coast of South America, a distance of two hundred miles by the shortest
route. Snakes often frequent trees, and might thus be conveyed long
distances if carried out to sea on a tree uprooted by a flood such as often
occurs in tropical climates and especially during earthquakes. To some such
accident we may perhaps attribute the presence of these creatures in the
Galapagos, and that it is a very rare one is indicated by the fact that
only two species have as yet succeeded in obtaining a footing there.

_Birds._--We now come to the birds, whose presence here may not seem so
remarkable, but which yet present features of interest not exceeded by any
other group. About seventy species of birds have now been obtained on these
islands, and of these forty-one are peculiar to them. But all the species
found elsewhere, except one, belong to the aquatic tribes or the waders
which are pre-eminently wanderers, yet even of these eight are peculiar.
The true land-birds are forty-two in number, and all but one are entirely
confined to the Galapagos; while three-fourths of them present such
peculiarities that they are classed in distinct genera. All are allied to
bir