THE GLACIAL RANGE CONTRACTION, ETC. 115 



known northern limits in the British Islands. The 

 migrations of the Knot [Trijiga canutiis), the Sanderling 

 {Tringa arenarid), the Snow Bunting {PlectropJicnax 

 nivalis), and the Wheatear {Saxicola ccnantlie"), are 

 perhaps more northerly in this direction, more dominant, 

 stronger, than in any other part of Europe, Again, the 

 Great Skua {Stercoramis catarvJiactes) and the Manx 

 Shearwater {Puffinus angloruni) range along this route to 

 Iceland, and the Stormy Petrel {Procellaria pelagica) to 

 Greenland, yet all three species are absent from the 

 Scandinavian Peninsula — a fact which suggests a land or 

 ice barrier to eastern progress beyond the longitude of the 

 Shetlands in remote ages when the emigration north of 

 these species was in progress. These are profoundly 

 interesting facts. They admit of but one interpretation 

 — a greater extension of land surface between Greenland 

 and the British Area during earlier ages. The ques- 

 tion of the ancient land areas in the North Atlantic 

 scarcely comes into the subject of this work, but if the 

 present dispersal of birds be any guide to past physical 

 changes, there can be no doubt that a vast extension 

 of land southwards between America and Europe once 

 existed, and that too possibly during Tertiary time. 



Our next table will indicate the two dominant lines of 

 Post-Glacial Emigration in the extreme west of Europe 

 — one extending to, and by way of, the British Islands 

 to Scandinavia, principally to Norway ; the other by 

 way of Belgium, Holland, and West Germany to Den- 

 mark and Scandinavia, principally to Sweden. 



