h, however, lends
additional force to the argument. New Zealand is sometimes classed as an
oceanic island, but it is not so really; and we shall discuss its
peculiarities and probable origin further on.

* * * * *

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CHAPTER XVI

CONTINENTAL ISLANDS OF RECENT ORIGIN: GREAT BRITAIN

Characteristic Features of Recent Continental Islands--Recent Physical
Changes of the British Isles--Proofs of Former Elevation--Submerged
Forests--Buried River Channels--Time of Last Union with the
Continent--Why Britain is poor in Species--Peculiar British
Birds--Freshwater Fishes--Cause of Great Speciality in Fishes--Peculiar
British Insects--Lepidoptera Confined to the British
Isles--Peculiarities of the Isle of Man--Lepidoptera--Coleoptera
confined to the British Isles--Trichoptera Peculiar to the British
Isles--Land and Freshwater Shells--Peculiarities of the British
Flora--Peculiarities of the Irish Flora--Peculiar British Mosses and
Hepaticae--Concluding Remarks on the Peculiarities of the British Fauna
and Flora.

We now proceed to examine those islands which are the very reverse of the
"oceanic" class, being fragments of continents or of larger islands from
which they have been separated, by subsidence of the intervening land at a
period which, geologically, must be considered recent. Such islands are
always still connected with their parent land by a shallow sea, usually
indeed not exceeding a hundred fathoms deep; they always possess mammalia
and reptiles either wholly or in large proportion identical with those of
the mainland; while their entire flora and fauna is characterised either by
the total absence or comparative scarcity of those endemic or peculiar
species and genera which are so striking a feature of almost all oceanic
islands. Such islands will, of course, differ from each {332} other in
size, in antiquity, and in the richness of their respective faunas, as well
as in their distance from the parent land and the facilities for
intercommunication with it; and these diversities of conditions will
manifest themselves in the greater or less amount of speciality of their
animal productions.

This speciality, when it exists, may have been brought about in two ways. A
species or even a genus may on a continent have had a very limited area of
distribution, and this area may be wholly or almost wholly contained in the
separated portio