Sir H. H. Hoicorth — The Baltic — The Litorina Sea. 315- 



Thus, in the black clays at Neder Kalix, at the very head of the 

 Bothnian Gulf, there have occurred Tellina balthica, which is now- 

 found living as far north as Umea ; Mytilus ednlis, whose northern 

 living range is Ulfon, south of Ornskoldsvik ; Cardium edule and 

 Hydrobia ulvcB {Paludinella balthica), which occur living at Kristine- 

 stad in Finland ; and Litorina rudis, var. tenebrosa, which does not 

 now extend beyond Bornholra. Litorina litorea, which is found in 

 the raised beds north of Hudiksvall, and which Loven and Erdmann 

 thought no longer lived in the Baltic, is still found living around the 

 isle of Rugen. 



Bissoa membranacea (var.), which now only reaches the meridian 

 of Zealand in Denmark, and therefore the Western Baltic, has been 

 found in the shell-beds of the Aland Islands and on the opposite 

 coast of Sweden. Scrobicidaria piperata, which is not known living 

 further than Wismar Bay, has occurred in the shell-beds of Nortli 

 Gotland. Spirorbis borealis, not now found further than about 

 Ystad, where Munthe says he found it on Mytilus, has been found in 

 the shell-beds of Gotland and Upsala. 



Membrauipora pilosa,. var. membranacea, whose furthest living 

 limits are Kristinestad in Finland, and Ulfon, between Hernosand 

 and Ornskoldsvik, in Sweden, has been found fossil by Munthe as 

 far north as Skelleftea in company with Mytilus and Tellina, and with 

 the leaf of a spruce fir. 



The disappearance of Litorina and Eissoce from the island of 

 Gotland was coincident with the introduction of Limncea ovata 

 into the Baltic fauna. Loven found it in some cases associated in 

 the shell-beds with the Litorinas, and he accordingly separated 

 these IJtorina beds into two horizons, one marked by the presence 

 of Limncea and the other b}'^ its absence. This invasion of 

 a mollusc (the LimncBa), which can only tolerate a certain amount 

 of brackishness in the water (Munthe says it lives in water with 

 l-rs" parts of salt at Malmo), is another proof of the change in regard 

 to salinity which has occurred in the Eastern Baltic since the later 

 beds on its borders were deposited. This is again supported by the 

 change which has taken place in the" shells themselves, no doubt due 

 to the same cause. Thus Lindstrom found that the specimens of 

 Cardium edule found in the shell-beds of the Island of Gotland 

 were larger than those now living there. 



Again, Munthe says that mussels of about 52 mm. in length, 

 corresponding to those now found at Riigen, are met with in the raised 

 shell-beds as far north as the Skelleftea district of Sweden ; and he 

 concludes that as the fauna of these Litorina beds, from the most 

 northerly part of the Bothnian Gulf down to Gotland, corresponds 

 most nearly to that of the present Baltic between Bornholm and 

 Warnemilnde, the hydrographic character, especially in regard to 

 salt of the Baltic Litorina sea, corresponded to that now existing 

 in the district in question, which has a proportion of salt at the 

 surface of 0"78-l-2 per cent. Elsewhere he says : " The fauna that 

 inhabited the Baltic in the Litorina time from the most northerly 

 point of the Bothnian Gulf down to Gotland corresponds most nearly 



