338 Sir H. H. JSoivorth — The Baltic — The Ancylus Sea. 



In regard to the marine diatoms and their distribution there is 

 more than one ambiguity. Munthe has, however, concluded from 

 a minute examination of the problem that they point to a greater 

 saltness in the Litorina sea than in the Baltic nowadays, and he 

 adds that an investigation of certain recent samples taken from 

 the South Baltic and adjacent regions proves that the diatomaceous 

 flora of the Litorina sea has roughly its closest parallel nowadays in 

 about the same region as its molluscan fauna (id., p. 32). 



Having defined the extent and condition of the Eastern Baltic in 

 the so-called Litorina time, we will now try and carry the story 

 a little further. The older inquirers, and notably Loven and 

 Erdmann, argued that the Litorina sea was the direct continuation 

 in situ of an older so-called ice sea, which was marked by the 

 presence of Yoldias and other northern shells. 



This was a mere speculation, however, since nowhere had a deposit 

 been found showing a graduation or change from one set of con- 

 ditions to the other, nor had any traces of the so-called Yoldia beds 

 been found over a very large part of the area where the former 

 presence of the Litorina sea was well established. 



In 1887 Munthe published a very important paper condensing 

 the results of his inquiries in the island of Gotland. In this paper 

 he first definitely showed that the views of Loven and the older 

 investigators of the history of the Baltic could no longer be main- 

 tained. He proved, in fact, that instead of the Litorina sea being 

 a direct successor of the so-called Yoldia or ice sea it was preceded 

 over a large part, if not all the Baltic area, by a condition of 

 things in which the Baltic formed a large fresh-water lake. To use 

 his own words, " it became evident that the Litorina fauna was 

 a completely distinct fauna and immigrated to the Baltic com- 

 paratively late, and could scarcely be supposed to have entered by 

 any other route than that of the Sound and the Belts." The 

 importance of this conclusion justifies me in giving its history in 

 some detail. 



The first step in defining the problem was taken by Schmidt in 

 an addition to G. von Helmersen's memoir on the diluvial beds of 

 Eussia, published in the Memoirs of the St. Petersburg Academy in 

 1869. Schmidt pointed out that in Esthland, in the lower parts of the 

 country, and in the former inlets of the Wick, there is a stratified 

 dark clay, sometimes occurring alone, and sometimes covered with 

 fine or coarse sands containing shell fragments, like that now being 

 deposited in some places by the sea, and which has its equivalent in 

 Sweden in the old inlets of the Malar Sea. Schmidt declared this 

 deposit as it occurs in Esthland to be of fresh- water origin, and he 

 said it there everywhere covers the widely spread angular gravel 

 known to the natives as Eichk or Plink. He goes on to say that 

 while in the raised beaches and terraces and deposits on the coast 

 of Esthland remains of marine shells occur, these are not found in 

 the interior of the country. They overspread the lowlands of the 

 islands of Dago, Worms, Nuckii, and the neighbourhood of Hapsal. 

 In Dago they occur at a height of 30 or 40 feet above the sea-level, 



