29 



The Norwegian Forms of Lithothamnion, 



By 

 3sÆ. Poslie. 



(With 23 Plates). 



The following account is intended to comprise all the spedes 

 of the algal genus Lithothamnion (including Lithophyllwm) at 

 present known to occur on the coast of Norway. It is founded 

 on a considerable number of specimens (more thousand), most of 

 which I have gathered myself in different tracts especially along 

 the northern part of the coast. However, of some of the species 

 I have seen only a few, or even but a solitary specimen. The 

 most northern part of the coast is in this respect tolerably well 

 known, except Lofoten and Vesteraalen in Nordlands Amt and the 

 greater part of Tromsø Amt. The Christiania- and the Trondhjem 

 Fjord also is råtner well known. But the other parts and especially 

 the very long western and south-western stretch of coast from Hite- 

 ren or Christiansund N. to Lindesnes and eastward off Christiania 

 is very littie searched and long stretches quite unknown. There- 

 fore, still rnuch remains to be done, not only in regard to the 

 Lithothamnia, but the marine algæ in all. 



The limits between the species are as a rule not easily drawn, 

 and often still more difficult without a greater number of specimens 

 from different tracts for comparison. A form may appear rather 

 well marked in one locality, but in another transitions to other 

 forms may be rather common, and one and the same species often 



