284 PREHISTORIC EUROPE. 



boulder-clay has yielded Mytilus edulis, Tellina halthica, Mactra 

 subtruncata, Mya (fragments), Littorina, Littorinella, Chenopus 

 (Aporrhals) pes-pelicani, Bulla, Balanus, Valvata, Cythere lutea. 

 The presence of the freshwater Valvata clearly indicates the 

 proximity of some land-surface from which it was washed down. 

 In connection with this it is worth noting that. Mobius has 

 chronicled the discovery of an atlas of Bos primiyenius in the 

 upper boulder-clay at Ellerbeck. 1 Underneath the lower boulder- 

 clay occur well-bedded clays {Bdnderthone) containing only a 

 few sporadic stones, most of them angular and consisting of red 

 felspar, granite, and gneiss. These stones, according to Penck, 

 have probably been derived from the wreck of a still older 

 boulder-clay, on the same horizon as the third boulder-clay of 

 Mark Brandenburg. It is remarkable, he says, that the beds 

 underlying the second boulder-clay should yield similar evidence 

 over so wide a region. The Bdnderthone of Danzig, Pomerania, 

 Berlin, and Holstein, all contain fragments of northern rocks, 

 and some of the clays at least are of freshwater origin. He 

 therefore would assign their formation to an interglacial epoch 

 following after the dissolution of the first ice-sheet, when the 

 ancient bottom-moraine was highly denuded, and its materials 

 re-arranged and re-distributed, gathering here and there in 

 lakes, and also perhaps in the sea. 



According to Forchhanniier 2 there are no fewer than four 

 boulder- clays in Denmark, separated by intercalated beds of 

 sand and clay ; and Puggaard has shown that there are three 

 tills displayed in Moen. From beds between the two lower 

 boulder-clays of that island the last-named geologist obtained 

 Tellina halthica, Venus ovata, Cyprina islandica, Cardium edule, 

 and Turritella sp. As I have already stated, it was Puggaard's 

 opinion that the great confusion visible in the sea-cliffs at 

 Moens Klint was caused by subterranean movements, but that 

 it is due to the grinding and crushing action of the last ice- 



1 Schriften des naturwissensehaftlichen Vereinsfiir Schleswig-Holstein, 1878. 



2 Oversigt over det Kgl. Banske Vidensk.-Selslcabs Fork., 1843, p. 103 ; Bull. 

 Soc. Gtol. France, 1847, p. 1178. 



