The part certain lime-secreting marine algae play in the building of coral reefs and in the formation of banks was discussed chiefly at the end of the last and in the beginnig of this century. At that time it was already known that extensive parts of the sublittoral zone of the Arctic sea were covered by a luxuriant growth of Lithothamnion species. Kjellman states in 1883 (p. 96) that along the northern coast of Norway Lithothamnion soriferum “covers large spaces of the bottom in great masses”, and that off the shores of Spitsbergen and Nova Zembla in 10 to 20 fathoms of water Lithothamnion glaciale “covers the bottom in deep layers for several miles, and altogether determines the general aspect of the vegetation wherever it occurs”, whereas Lithothamnion norvegicum is said to form banks on the coasts of Iceland and of Greenland. Rosenvinge (1893, p. 772) reports that Lithothamnion ungeri forms banks on the coast of Iceland and of Greenland.