12 THE MIGRATION OF BRITISH BIRDS 



occur in the older Pleistocene deposits, but have not 

 been dug up in beds pertaining to the latest stage of 

 the Pleistocene Period. Nevertheless, the characteristic 

 Pleistocene fauna is well represented in the ' forest 

 bed ' of Norfolk by such animals as cave-bear, wolf, 

 fox, wild-boar, urus, maminoth, Irish deer, roe, stag, 

 beaver, and mole. The fauna of the ' forest bed ' is 

 thus intermediate between that of the Pliocene on the 

 one hand, and the Pleistocene on the other, and is more 

 closely allied to the latter than the former." Professor 

 Geikie continues : " Underneath the oldest known 

 boulder clay — that of Cromer in Norfolk — occur certain 

 fluvio-marine deposits, the plant remains in which be- 

 speak the kind of climate that characterized England 

 at the commencement of the first glacial epoch. That 

 .flora embraced Scots fir, spruce fir, yew, alder, oak, 

 birch, white and yellow water-lilies, bog-bean, common 

 sloe, etc. — indicating a climate perhaps a little colder, 

 but not essentially differing from that of Norfolk at 

 present. But as the plants are traced upwards through 

 the strata they were found by Mr. Nathorst to become 

 ■more and more stunted and meagre, until in a bed 

 immediately underlying the boulder clay he came upon 

 the Arctic willow {Salix polaris) and a moss {Hypiiiun 

 Uirgescens) now confined in temperate latitudes to the 

 highest alps." 



We possess but little reliable information respecting 

 the physical history of the British area during the 

 Glacial Epoch, and great difference of opinion prevails 

 among authorities thereon. Fortunately such history 

 does not very intimatel)' concern the subject of our 

 investigations, which in its entirety is amply accounted 



