47° PREHISTORIC EUROPE. 



they are true littoral accumulations. In Southern Norway- 

 similar shell-banks are found at various levels, from 50 feet or 

 so up to 150 or 200 feet above the sea. 



The postglacial beds of Finland and Northern Eussia have 

 been described by Krapotkin and Schmidt as consisting partly 

 of freshwater and partly of marine deposits — the former being 

 the older of the two series. After the retreat of the great 

 glaciers, or mer de glace, the surface of the ground was left 

 covered with extensive sheets of boulder- clay, and abundant 

 spreads and heaps of erratics, gravel, and sand. The Gulfs of 

 Finland and Bothnia are believed to have existed at the close 

 of the Glacial Period as great freshwater lakes — the terraces 

 which mark the ancient margins of the lakes being found, not 

 only in certain inland districts, but also upon some islands in 

 the Baltic (such as Mohn and Dago), at a height of 50 feet or 

 so above the sea. These terraces yield freshwater-shells {Lim- 

 ncea ovata and Ancylus fluviatilis), and similar terraces, indi- 

 cating the former presence of ancient lakes at higher levels, 

 have been traced in the interior of Finland up to a height of 

 150 feet. The whole region, which even now contains many 

 lakes, seems at the close of the Glacial Period, or the beginning 

 of Postglacial times, to have been covered over wide regions with 

 extensive sheets of fresh water. In many cases the natural dams 

 which held in these waters consisted of asar or great gravel- 

 ridges that were rendered water-tight by the mantle of loam 

 and silty clay which often cloaks their slopes. The different 

 levels occupied by the ancient lakes, as their confining barriers 

 successively gave way, are marked by terraces eroded in the 

 sides of the asar. 



It is remarkable that, notwithstanding the great height to 

 which marine late glacial and postglacial deposits have been 

 traced in Scandinavia, not a single sea -shell or any other 

 evidence of glacial or postglacial submergence has yet been 

 detected in the interior of Finland. Professor Loven 1 and other 



1 Ofv. af Kongl. Vet. Akad. Fdrh. 1861, No. 6. Professor Loven instances 

 the occurrence of certain arctic species which occur both in the Baltic and some 



