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 Conti- 
nent — Why Britain is poor in Species — Peculiar British Birds — Fresh- 
water 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 sub- 
sidence of the intervening land at a period which, geologically, 
must be considered recent. Such islands are always still con- 
nected 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 com- 
parative scarcity of those endemic or peculiar species and genera 
which are so striking a feature of all oceanic islands. Such 
islands will, of course, differ from each 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 intercom- 
munication with it; and these diversities of conditions will 
manifest themselves in the greater or less amount of speciality 
of their animal productions. 
