Ln Norw. Lith. 1 ) I subsumed the genus IMhophyllum as a 

 subgenus of LiihotJiamnion on the ground of the characters on 

 which the limitation of these genera used to be founded, namely 

 the development of the vegetative organs. At the time I did not 

 posses any specimen of the proper type of the genus. L. Jichenoi- 

 des, but I took my stand on it pursuant to another and rather 

 cognate representative. L. Lenormandi. I found it even to be 

 matter of doubt whether LithophyUum as it was) only on the 

 above mentioned foundation was to be 'considered a subgenus. At 

 the same time I looked, however, upon Jlelobesia (as it was) as 

 a genus the limits of which were rather well marked. But some 

 time after the publication of Xorw. Lith. I perceived certain pecu- 

 liarities concerning the reproductive organs of some species, after 

 which I was clear that the systematism of these calcareaus Algae 

 in most essential respects was to be based onry upon the repro- 

 ductive organs, as suggested by Solms Laubach and other 

 authors. This also in a large measure applies to the limitation of 

 species which already has been indicated in Xorw. Lith. On se- 

 veral motives 1 did not publish an\~thing about this before the 

 undermentioned Syst. Surv. 



ln 1891 when writing about fossil calcareous Algae, Dr. Roth- 

 pletz 2 ) proposed three groups of Lithothamnia. namely Archæo- 

 litJiothamiiion, LitJiotJiamnion and LitJwfhamniscum, the former 



1 M. Foslie. The X : r.vegian Forms of Lithothamnion. — Det kgl. r_orske 

 /enskabers SeJskabs Skrifter 1894. Trondhjem IS :. 

 thpletz, rrssile Kalkalgen. — Ze> 

 43. 1891. Pa°f. 295. 



