MARINE ALGA. 
II.-CORALLINACEA. 
sy M. Foss. 
LITHOTHAMNION COULMANICUM. 
Amone 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 Lithothamnion, 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 Fost. 
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 Fost. Nar. SIZE. 
particularly when attacked by animals or when covering extraneous objects. It is 
thin, in the specimens brought home the thickness not exceeding 800, frequently 
being less, or about 300n. 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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