POSTGLACIAL, 6rv., DEPOSITS OF CONTINENT. 471 



Swedish naturalists and geologists have shown that there is some 

 reason to believe that during late glacial times the Baltic had 

 direct communication with the Arctic Ocean, probably by way 

 of the Gulf of Finland and Lakes Ladoga and Onega to the 

 White Sea. Lake Onega, however, is said to be 280 feet above 

 the sea, and not a vestige of marine glacial or postglacial 

 deposits has been observed in its neighbourhood. The only 

 evidence of postglacial submergence which has been noted by 

 Eussian observers consists of certain deposits of gravel, sand, 

 and clay, which occur along the margins of the Gulfs of Bothnia 

 and Finland up to a height of 50 feet above the sea. These 

 deposits are charged with remains of the well-known Baltic 

 fauna. It would seem, therefore, that the movement of depres- 

 sion, which in postglacial times carried down the southern area 

 of Norway and Sweden to a depth below its present level of 

 500 feet or thereabout, died out northwards to such an extent, 

 that in the northern gulfs of the Baltic the sea covered only a 

 limited area of low ground in the maritime districts. 



The shell-bearing deposits of Norway are overlaid, according 

 to Kjerulf, by unfossiliferous accumulations of lighter-coloured 



of the Swedish lakes. Malmgren likewise gives a list of fish which are common 

 to the Baltic and the Arctic Ocean — Cottus scorpius, Cyclopterus lumpus, 

 Zoarcus viviparus, Gadus morrhua, Pleuronectes platessa, P. Jlesus, Liparis 

 barbatus, and Clupea harrengns, var. membras (Kritisk Ofversigt af Finnlands 

 Fiskfauna 1863, p. xi.) Some of these, such as the bullhead (Cottus scorpius), 

 the sucker (Liparis barbatus), and the variety of the herring, appear to be con- 

 fined to the northern reaches of the Baltic. It is thought that these species tell 

 strongly in favour of a recent direct connection between the Baltic and the Arctic 

 Ocean. Had they immigrated from the south into the Baltic it is supposed that 

 inherited instinct would have led them to return by the same way when the con- 

 ditions in the Baltic became less favourable. I must mention also that Loven 

 has noted the occurrence in the valley of the Dwina, to the east of Onega, of 

 deposits with arctic shells which go up to ajieight of 150 feet. Still, although 

 this evidence is suggestive it is not convincing. It may be that the arctic forms 

 in the Baltic are simply relics of the fauna which lived over the submerged regions 

 of Scandinavia during the deposition of the late glacial clays, when the Baltic 

 was as salt as the open ocean, and characterised by the presence of Yoldia (Leda) 

 arctica and its congeners. They would appear to come into the same category 

 as those high northern forms which are still found lingering in the deeper depres- 

 sions of the sea-bottom round our own coasts. The former direct connection of 

 the Baltic with the Arctic Ocean has yet to be proved. 



