MAEINE ALGJ5. 



II.-CORALLINACE^. 



By M. FOSLIE. 

 LITHOTHAMNION COULMANICUM. 



the Natural History collections made in the Antarctic regions by the 

 ' Discovery ' Expedition are some specimens of a calcareous alga, which has been 

 kindly sent me for determination. They proved to represent a species new to science 

 belonging to the genus LithotJiamnion, which I shall now describe. The species has 

 been shortly mentioned in " Det Kgl. norske Videnskabers Selskabs Aarsberetning " 

 for 1904, p. 16 (Trondhjem, 1905), under the name of 



LITHOTHAMNION COULMANICUM FOSLIE. 



The plant forms incrustations on pebbles. The crust is closely adherent to the 

 .substratum when young, but when older it is here and there rather easily detached, 



LITHOTHAMNION COULMANICUM FOSL. NAT. SIZE. 



particularly when attacked by animals or when covering extraneous objects. It is 

 thin, in the specimens brought home the thickness not exceeding 800/z, frequently 

 being less, or about 300/x. The shape of young crusts is frequently more or less 

 irregular, but now and then almost circular, and so also when older, but then the plant 

 sometimes fully surrounds the substratum. It is sometimes indistinct concentric 

 zonate, and the edge is crenulate or irregular. Several crusts are often found on the 

 same substratum. They may run into each other, in some cases not showing any 

 visible mark where the joining takes place, in others here and there forming slightly 

 elevated ridges. The nature of the surface is determined by that of the substratum. 

 If this is smooth the crust is also smooth, and shines slightly when young. Older 



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