244 HISTORY OF THE EUROPEAN FAUNA. 



the Northern Russian and German plains, and into it icebergs 

 discharged the detritus which had accumulated on them when 

 they were still Scandinavian glaciers. 



As regards the time of the arrival of the Siberian migrants in 

 Europe, the English Forest-Bed gives us an additional clue to 

 its determination. Since Siberian migrants are unknown from 

 earlier deposits than this, it is reasonable to suppose that they 

 arrived in England about the time when it was laid down. But 

 since they appear in Germany in the inter-glacial beds subse- 

 quent to the deposition of the lower boulder-clay, the former are 

 probably contemporaneous with the Forest-Bed. Some of the 

 deposits generally regarded as upper pliocene by British geolo- 

 gists would therefore have to be classed with the lower 

 continental boulder-clay as lower pleistocene. In connection 

 with this theory some interesting faunistic data are given 

 which seem to support it. 



In conclusion, the former presence of Arctic plants in Central 

 Europe and their bearing on the climatic problems are 

 discussed. 



