Sir IT. H. Koworth — The Baltic — The Litorina Sea. 317 



found in the same beds in 1859 at Grason in Roslagen (id.). The 

 black clay resembles the buttery clay which underlies the flat levels 

 of the lands round the Wash in East Anglia. 



Erdmann tells us that this black clay is often found intercalated 

 with the beds of gravel and rolled stones which form the covering 

 mantle of the asar, and in some cases this mantle is so full of shells 

 as to be formed almost entirely ot them. These banks of shells 

 often occur without clay, and interbedded among the upper layers of 

 the gravels and sands, and sometimes with clay which underlies 

 them or with the so-called akerlera which covers them. The 

 shells contained in them are the same as those in the black clays. 

 Erdmann gives a figure of the as of Enkoping, where these shell- 

 beds occur on a great scale, intercalated with beds of gravel, stones, 

 and sand. At one place the shell-bed, several feet thick, consists 

 almost entirely of comminuted shells of Mytilus edulis and Tellina 

 balthica. The shell-beds are separated by beds of gravel or barren 

 clay and sand. Erdmann says that in a great cutting through this 

 as at Enkoping thei'e is found the typical black earth containing 

 shells of Mytilus edulis. The epidermis of the Mytilus is singularly 

 well preserved in many cases when the shells themselves have 

 entirely disappeared (id., pp. 96, 97). After the work just cited 

 was written Erdmann recognized these beds as far as Linde at the 

 head of a lake of that name 130 miles west of Stockholm, and to 

 a height of 230 feet above the sea-level, which, Lyell argues, shows 

 that the Baltic has been separated for a long time, as now, from the 

 ocean (" Principles," 12th ed., p. 194). 



Again, in 1873, Gum^lius reported beds with shells of M. edidis 

 and T. balthica, ranging as high as 250 feet above the sea-level, at 

 Bondsio, near Hernosand, at the mouth of the Angerman River, and 

 at Avoka, near the frontier of Medelpad. Munthe apparently found 

 these beds at Hernosand at a height of 330 feet above the sea 

 (" Sommarkursernai, Upsala," 1893, p. 16). Gumeelius mentions 

 T. balthica, il. ulvce, a L. rudis (since shown to be rudis), and 

 N. fluviatilis as found there (G. F. i Stock. For., i, 233-4). Hisinger 

 found the same beds at Djekneboda in Westerbotten ; Freidholm, 

 at Neder Kalix at the head of the Bothnian Gulf, at the height of 

 at least 110 feet, and Hogbom, at Lofanger, and Eicklea, from 80 to 

 100 feet above the sea-level. These contained fragments of Mytilus, 

 and more sparsely Tellina balthica. 



At Alnon, in 62° 28' N.lat., Munthe found the shell-beds at the 

 height of 77 metres, at Ornskoldsvik at 60 metres, and at Neder 

 Kalix at 51 metres (De Geers, G. F. i Stock. For., xii, 104). 



On the borders of Finland and its islands similar beds have also 

 been found. They were first described from the Aland Islands as 

 far back as 1767 by Tuneld, and since by Holmberg and others. 

 Eichwald described similar deposits in a fine sand along the coast 

 near Helsingfors, and especially mentions Mytilus edulis and Tellina 

 balthica. both small, Paludina balthica (i.e. Hydrobia ulvce), and 

 Nerita fluviatilis as found in it. He mentions similar deposits from 

 Vora Kyrka in the province of Vasa, on the east of the Bothnian 

 Gulf, as also affording fragments of Mytilus edulis. 



