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 — 

 Trichoi)tera Peculiar to the British Isles — Land and Freshwater Shells 

 — Pecidiarities of the British Flora — Peculiarities of the Irish Flora — 

 Peculiar British Mosses and Hepaticee — 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 



