THE BALTIC SEA 



339 



Arctic-Mediterranean 42 per cent, for the Baltic Sea alone the first group 

 comprises only 22 per cent and the second 70 per cent. 



Comparing the Baltic Sea fauna with that of the east Greenland fjords 

 G.Torhson( 1934) makes a good appreciation of the Arctic nature of theformer. 

 He points out that the similarity between the Greenland biocoenosis Astarte 

 borealis and the corresponding one from the Belt and the Baltic Sea is re- 

 markable. In the latter we again find : Macoma calcarea, Astarte borealis, A. 

 banksi, A. elliptica, Modiolaria nigra, Priapulus caudatus, Scoloplos armiger 



Fig. 168. Occurrence of fossil Greenland seal on the shores of the Baltic and 

 its contemporary habitat in the Arctic basin (Ekman, 1930). 1 Sites of feeding 

 migrations ; 2 Breeding areas ; 3 Routes of migration ; 4 Occurrence in fossil 



state. 



(in eastern Greenland Sc. cuvieri) and some other polychaetes. In the shal- 

 lower places of the Baltic Sea Macoma calcarea is replaced by M. baltica, 

 remaining, however, in deeper patches. Torhson thinks that the fauna of the 

 deep-water zone of the Baltic Sea and the Belt corresponds to that of the 

 coastal zone of the eastern shores of Greenland and represents the Arctic relict 

 biocoenosis in the Baltic. 



Many Arctic forms have moved their habitat to the north, leaving only 

 their fossil remains in the Baltic Sea area (Fig. 168). Thus Phoca groenlandica 

 was common in the Baltic even during the Littorina period, and was abun- 

 dantly used in the food of primitive man. It is not clear how the Greenland seal 

 could survive the fresh-water phase of the Ancylus Lake and the warm Littorina 

 phase. Ekman considers this seal a Yoldian Sea relict in the Littorina Sea. 



When and in what way did the Ice Age marine ancestors of the present- 

 day relicts penetrate into the Baltic Sea? The answer to this must be sought 



