316 Sir H. H. Howorth—The Baltic— The Litorina Sea. 



to the present fauna of the comparatively limited area of the same 

 sea that lies between Bornholm and Warnemiinde " (op. cit., pp. 5, 6). 



Although it is clear, therefore, that the water of the Baltic has 

 been growing more brackish, it is quite clear also that in tlie 

 Litorina time it was also brackish but not to the same extent. 

 Tills follows from the fact that the shells found in these beds are 

 Smaller, in some cases very much smaller, than those of the same 

 species found in the open sea, a fact which Nathorst has shown 

 graphically by giving us side by side figures of the Baltic Cardium 

 and a Litorina and the same shells from the open sea. It follows also 

 from the occurrence of two brackish- water shells in these beds — the 

 Paludinella balthica, which is not a salt but a brackish- water shell, 

 and the Neritina fluviatilis. 



Having established that the waters of the Eastern Baltic have 

 become less salt and more brackish in the most recent geological 

 period, i.e. that now current, the next question that arises is as to 

 the cause for this change. One thing is clear enough, namely, that 

 when the Litorinas were living in the Eastei'n Baltic it covered 

 a larger space and contained a larger quantity of water. This is 

 plain from the raised beds in which the Litorinas occur, which must 

 then have been submerged. 



The true Litorina sea extended as far as the Sound, for the beds 

 found virtually at the sea-level at Malnio contain Cardiums and 

 Litorinas like those in the Baltic. The same is the case with the 

 other side of the Sound, where at Kordam the beds occur with 

 Cardium edtde, Mytilns edidis, Tetlina balthica, Litorina litorea, and 

 Nassa reticulata (Nathorst, Sveriges Geologi, 277). 



When we go northwards into the district of the Malar Sea we 

 find these shell-beds at a much higher level. Thus, Erdmann in 

 1868 gave a list of some of the places where clay with similar 

 shells had occurred in the district of the Malar Sea, with their height 

 above the sea and their distance from the Baltic (Sver. Geol. 

 Undersokning, i, 42) : — 



North of Orebro ... 



South of Totiasjon, near Arboga 



South of Kungsor .. . 



Hasslo, east of Westeras ... 



Enkbping ... 



North of Husby Church, in Nykopiugslan 



Upsala, Slottsbacken 



Sodertelge ... 



Erdmann tells us that at Nyiiker, north-east of Upsala, and at 

 Skattmanso, a few miles north of Enkoping. there have also occurred 

 in the black clays remains of the bullhead (Cottus scorpius), 

 a characteristic fish of the present Baltic. Nathorst tells us that the 

 variety of the perch (Ferca fluviatilis) known as the Baltic perch 

 has been found with Mytilns at Stureplan, near Stockholm (see 

 Sveriges Geologi, 271) ; a grey seal [Hnlichoerus gryphus) was found 

 in Gotland, while a skeleton of the whale LscJirichtius robustns was 



