340 Sir H. H. Howorth—The Baltic— The Anci/ius Sea. 



whether the fresh-water beds are older than the marine (now called 

 Litorina beds) or not. He adds, however, " Vielfach sieht man 

 aber marine Sande auf Banderthon aufliegen, der, wie gesagt 

 stellenweise Becken bildet, die von Ancylusschichten umsaumt sind"; 

 and says further, what I cannot quite understand, "Die hohe lage 

 dieser Schichten auf Mohn sprecht dafiir, dass bei ihres Bildung die 

 Insel noch nicht von Festlande getrennt war. Vielleicht war den 

 ganze Eiga'sche Meerbusen ein Siisswasser becken " (op. cit., p. 266). 



In 1884 Munthe recognized similar fresh-water beds at the height 

 of 130 feet south-west of Wisby in the island of Gotland, in which he 

 observed Zimnaa ovata and Pisidium ovatum. 



In the same year Holm, in a letter to Hoist, implied the occurrence 

 of these fresh-water beds in Gotland, and also foretold their 

 occurrence in Oland (see Hoist, Sver. Geol. Unters., No. 180, 

 p. 96, note), which he definitely proved two years later in a paper 

 published in the Geol. Foren. Stock. Fork, 1888, vol. x, p. 365. 



In a visit to Gotland made in 1886 and 1887 Munthe found 

 similar deposits at a height of 100 to 150 feet marked by the 

 presence oi Ancylus fluviatilis. These beds consisted of typical open 

 beaches with pebbles and sand. Munthe tells us that in 24 sites 

 where they occurred in Gotland Limncea ovata was represented in 

 23, Ancylus in 19, and Pisidium in 10. In addition there were 

 found in them Limnma palustris, Planorbis contortus and marginatus, 

 Valvata crista ta, Bythinia tentaculata, several other species of 

 Pisidium, including amnicum, pallidum, fossarium, pnsillum, var. 

 major, and three species of Ostracoda, Cypris reptans, Candona 

 compressa and Candida. 



Munthe gives a map of the localities in the south-east of Gotland, 

 such as Nar, Lau, and Burs, as well as the limestone ridges called 

 Burgen where these deposits have been found. 



In Oland Hoist says that the Ancylus and Litorina beds are found 

 well developed in the villages of Morbylanga, Kesmo, and Vickleby, 

 on the western side of the island, although they are not so abundant 

 there as they are on its eastern side (Sver. Geol. Und., No. 180, 

 p. 95, note). 



The occurrence of these fresh-water deposits in so many localities 

 upon open beaches facing the sea, on the mainland as well as on the 

 islands in the Baltic, enabled Munthe to make the very important 

 generalization embodied in his paper already cited, and published in 

 1887, namel}', that the Baltic was once a fresh-water sea or inland 

 lake, and that this stage immediately preceded the Litorina stage in 

 its history, since the Litorina beds are found overlying the fresh- 

 water ones. From these beds being especially characterized by the 

 shell Ancylus he gave them the name of Ancylus beds, and the sea 

 in which they were found the name of the Ancylus sea. 



The Ancylus has an outward resemblance to the limpet, and has 

 sometimes been called the fresh-water limpet. It was, in fact, called 

 a Patella by Linnseus. The northern geologists give the Ancylus 

 we are discussing the specific name oi fluviatilis, but this involves 

 a difficulty. The shell so called is apparently limited in its habitat 



