202 



CORALS 



is more difficult, but reference to that will be made at a later 

 stage. 



The most familiar form of Lithothamnion is perhaps 

 the flat encrusting species (L. lenormandi) frequently found 

 encrusting stones and rocks at low tide on the British 

 coasts. It is usually of a dark salmon-red colour but becomes 

 pink or blanched when exposed to the sunlight. In deeper 

 water off our coasts another species {e.g. L. fascicnlatum) 

 may be found, sometimes in immense quantities, forming a 

 complete carpet over considerable tracts of the sea-bottom-. 



This is a branched 

 fasciculate form. 



Another form such 

 as that represented 

 by Lithothamnion 

 dimorphuni, also 

 found off the British 

 coasts, consists of 

 large irregular lumps 

 of coral several inches 

 across with a surface 

 covered with short 

 papillate or mammil- 

 late processes (Fig. 



Fig. io::. — Lithothamnion dimorphmn from west 

 coast of Ireland. Nat. size. 



102 



The importance of 

 Lithothamnion lies in its widespread distribution and extra- 

 ordinary abundance. Thus on the coast of Spitzbergen and 

 Nova Zembla, Litliothamnion glaciale covers the bottom in 

 deep layers for several miles. L. ungeri forms banks off 

 Greenland. In temperate regions we have the Litho- 

 thamnion beds on the British coasts and such instances as 

 the NuUipore banks of the Gulf of Naples, which are mainly 

 composed of Lithothamnion ramulosum. 



In the Tropics, reference has already been made to the 

 abundance of Lithothamnion on the reefs of Timor. Off 

 Tahiti rounded masses of this coral were found in lo 

 fathoms of water in such abundance that the dredge came 

 up tilled with them. Gardiner has also referred to its 



