462 Proceedings of the Royal Irish Academy. 



(p. 473), viz., the former continuation of the Scandinavian coast- line 

 in a north-westerly direction to Spitsbergen and North Greenland 

 (see map, p. 461). The cold waters of the Arctic Ocean did not com- 

 municate at all with'the Atlantic at the time when the above-mentioned 

 changes occurred in Northern Europe, but they poured into the Baltic 

 and the German Ocean, which was then a closed bay, and brought 

 with them the characteristic fauna of the Arctic regions. 



The Aralo-Caspian communicated with this large northern sea, 

 which had formed on the North European lowlands, and which we 

 may call the " North European Ocean," at a time immediately pre- 

 ceding the deposition of the upper boulder-clay. But the barrier which 

 prevented the Siberian fauna from entering Europe was the strait or 

 straits which connected the two seas. We can, therefore, accurately 

 fix the period of the beginning of the migration, for it must have 

 occurred as soon as this barrier disappeared ; or, if we are able to 

 ascertain stratigraphically the first appearance of the Siberian immi- 

 grants in Central Europe, the disappearance of the barrier must have 

 immediately preceded that period. 



Thanks to the researches of Prof. Neliring (62 3), who gives us a 

 vivid picture of Siberian life in Europe as reconstructed from his 

 discoveries of vast stores of fossil remains in Northern Germany, we 

 now know that the migration from Asia took place undoubtedly after 

 the deposition of the lower boulder-clay, or, as we might say, after 

 the first Glacial Period. Prof. Nehring (62 ^•, p. 223) seems inclined to 

 think that the migration occurred immediately after the deposition of 

 the lower boulder-clay, that is to say, during the Interglaciul phase of 

 tlie Glacial Period. Prof. Penck agrees with liim in so far as that he 

 regards the "Loess " in which these remains are found as belonging 

 to the Interglacial Age (66c, p. 15). However, we also know that 

 m England remains of Siberian Mammals occur from the Eorest-bed 

 iipward, whilst none are found in older strata. It seems safe to 

 conclude, therefore, that the Siberian migration took place after the 

 deposition of the^lower continental boulder-clay, and during or just 

 previous to the formation of the Forest-bed. But the latter has been 

 lately recognized as a pre-Glacial formation, and it certainly underlies 

 the English boulder-clay. How can we then reconcile these two 

 apparently so very contradictory conclusions — that a migration which 

 undoubtedly set out from the East arrived in Western Europe before 

 it reached Central Europe ? 



I have shown in a previous Paper (7Gc, p. 448) that such was 

 certainly the case with some Southern Asiatic Mammals, which entered 



