o
distinct routes. All entered from Asia Minor, which is proved to have
been connected with Greece until recent geological times. From here some
seem to have proceeded straight west, others northward. Further study
reveals the fact that the first route was followed by a much older set
of migrants at a time when the Mediterranean area was greatly different
from what it is at the present day. Greece was then joined to Southern
Italy, Sicily, and Tunis. The latter was also connected with Sardinia
and Corsica, and the Straits of Gibraltar did not exist. Under such
geographical conditions a direct migration on land from Southern Greece
to Spain was not only possible, but was actually undertaken by a very
large number of Oriental species.

FOOTNOTES:

[1] Since writing the above account, Mr. Boulenger, in his new work on
the Batrachia of Europe, has accepted the specific distinctions between
the two fire-toads.

[2] In some cases the accuracy of this view is proved by fossil
evidence, _Helix rotundata_, a common and widely spread British species,
having been found in miocene strata near Bordeaux.

[3] There are a great many instances of discontinuous distribution among
Oriental Invertebrates. Thus the Freshwater Crab (_Thelphusa
fluviatilis_) occurs in Southern Italy, Greece, Turkey, Cyprus, and Asia
Minor. Another crustacean--a Freshwater Crayfish--(_Hemicaridina
Desmaresti_) inhabits Spain, Corsica, Sardinia, Sicily, and Asia Minor.

CHAPTER VII.

THE LUSITANIAN FAUNA.

Under the Roman Emperor Augustus, the Spanish peninsula was divided into
three provinces, one of which--namely Lusitania--occupied a large
portion of the present area of Portugal. The term "Lusitanian" is
therefore almost synonymous with Portuguese, but it has frequently been
applied by zoologists and botanists in a much wider sense, so as to
vaguely include the extreme south-west of Europe without any definite
limits. Neither do I propose to restrict the term to everything found
within the borders of Portugal. For the sake of convenience, we may
designate as Lusitanian forms those animals and plants which have
migrated to Central, Southern, or Northern Europe from South-western
Europe. They may really be North-west African species, or they may have
originated on land which lay to the west of Portugal, and which is now
mostly buried beneath a deep sea. Nevertheless, we have received them
from the extreme south-western portion of our continen