15 72 Proceedings of the Royal Irish Academy. 



these found in the British Isles. At Morlaix and Oonoarneau there is " coral 

 sand" or " Maerl," and, as in Ireland, this is used for manure. Lemoine 

 ('10) has also published a detailed account of the biology of the plant. She 

 notes that at Coucarneau the bottom of the bay is practically covered with 

 I. calcareum, and fragments of living fronds are continually cast up by the 

 waves. Several " coral beaches " occur on the islands of the Glenan 

 Archipelago, but there, as at Mannin Bay, the fragments washed ashore are 

 mostly dead. 



In the Arctic seas, Kjellmann writes of large areas, in 10 to 20 fathoms, 

 covered with Lithothamnia, of which L. glaciale and L. sori/erum are abundant. 

 At Mussel Bay in Spitzbergen, I. glaciale is said to cover the bottom to an 

 extent of 4 to 5 square miles ; whilst off the north of Norway and on the 

 coast of Iceland, L. Ungcri is abundant. In the former country banks of 

 I. norvegicum also occur. The association is represented in Greenland by 

 L. Ungcri. In the south of Norway the floristic features are more in agree- 

 ment with those of Britain, and L. calcareum becomes prominent. An 

 association composed largely of this species has been described by Gran for 

 Kristianiafiord (.'93). 



Reference must be made (though it is outside our usual circle of com- 

 parison) to Madame Weber van Bosse's account of the Lithothamnia of the 

 " Siboga " Expedition ('04). A very luxuriant vegetation exists in the shallows 

 and reefs of the Malay Archipelago, and several communities on different 

 types of ground are referred to. A description is given of a locality where 

 the Lithothamnium knolls are rolled backwards and forwards between the 

 islands by the tidal current, whilst in other parts of the same channel they are 

 heaped up in banks. Two photographs are reproduced of an extensive bank 

 of L. erubescens var. Haingsisiana, which Madame Weber describes as being 

 " covered as far as the eye can reach by the pretty, beautifully pink-coloured 

 knolls, which are heaped so close together, that while walking one crushes 

 them continually, making a peculiar noise as of broken china " (I.e., p. 5). 



Geological Importance. — In localities where masses of Lithothamnium 

 accumulate on the sea-bottom, these algae play an important part in rock- 

 formation, and masses of limestone containing well-preserved Lithothamnia 

 occur in various geological strata. Structureless limestone also may be 

 derived from the same source, for Walther, working at Naples, showed that 

 the structure of recent Lithothamnium nodules is gradually obliterated by the 

 action of percolating water. The literature on the subject is scattered ; but 

 Seward's paper ('94) gives a general summary with a full bibliography ; 

 and a brief but up-to-date account has just been published by Lemoine 

 (11 b). 



