306 PEOP. HULL, LL.D., F.E.S., ON THE SUBMERGED TERRACES 



mology of Iceland have been described in the Transactions 

 of this Institute by the Rev. Dr. Walker, F.L.S.,* and his 

 observations bear witness to the former land connection of 

 Iceland with the British Isles. His remark that "the first 

 thing that strikes a visitor from the latter country is not the 

 number of Arctic species, but the great abundance of plants 

 that are very rare and local in Britain, such as Saxifraga 

 ccespitosa, Liclmis alpina, and Erigeron alpinum, etc." The 

 disappearance of the former glacial conditions from the 

 British Isles and their continuance in Iceland accounts for 

 the remarkable abundance of the plants referred to. 



The very ample surve}'' of the insects given by Dr. Walker 

 leads him to the following conclusions :— 



1. The total absence of butterflies. 



2. „ „ orthoptera. 



3. Neuroptera only represented by Phryganid(x. 



4. The most abundant tribes of insects in Iceland are 



moths and Diptera. 



On the whole, the insect fauna, as Avell as the flora, of this 

 island bear a remarkable affinity to those of Scotland-t As 

 regards Greenland, while some of the forms are European, 

 others are American, a few being purely Arctic, and Wallace 

 includes it in his Nearctic province. At the same time about 

 one-third of the vertebrates are European,! and indicate a 

 former connection with that continent, though not to the 

 close extent of that of Iceland. 



Now, we must not forget that this community of fauna 

 and flora is characteristic of existing genera and species, 

 and indicates a very recent physical, or land, continuity. 

 It may date back, perhaps, as far as Pliocene times, passing 

 into Recent, but not earlier ; and if this be so, we have to 

 consider to what extent the bed of the Atlantic Ocean 

 requires to be raised in order to establish such a land 

 connection, or in other words the amount of recent sub- 

 mergence which it has undergone ; we have also to deter- 

 mine the tract of the ocean over which the continuity of 

 land surface formerly existed. 



The remarkable results established by American natura- 

 lists regarding the submerged terraces and river valleys 



* Trans. Vict. Inst., vol. xxiv, p. 205. 



+ Supra cit., p. 241. 



X Wallace, supra cit., vol. ii, p. 138. 



