186 



latter is referred in this paper, viz. L. crassum Phil., or perhaps 

 partly belong to L. fruticulosum. But on the other hand those 

 referred to L. polymorphum do not belong to this species in the 

 sense here tåken. They not unlikely are identic partly with the 

 same species as the above mentioned partly L. incrustans f. Har- 

 veyi. They, however, ought to be compared with living specimens, 

 as the same species are considered „ still to be found living in the 

 Bay of Dublin, but apparently not any longer in the mouth of the 

 River Liffey". 



The Lithothamnion banks in the sea are extensive not only 

 in horizontal but also in vertical direction, in larger banks the lower 

 layers consist of dead specimens, by and by increasing upwards, 

 and in this respect they correspond with the coral-reefs of the 

 tropics. With us I have seen various such banks, which, especially 

 in sounds and branches of fjords, have increased so much in ver- 

 tical direction, that the top of the bank has been but veiy little 

 below the present level of low-water and by lowest neap tides 

 even partly laid dry. In places with rapid tides these banks also 

 give rise to a greater accumulation of mud. I got numerous spe- 

 cimens from Vardo obtained by the harbours stirring up mud. 

 Some few of these have been living, and belong to L. fruticulo- 

 sum f. glomerata. The other and very greatest part of the collec- 

 tion consists of dead individuals and belong to a species which on 

 the one side reminds one of certain forms of L. fruticulosum ; but 

 on the other side by the rather regular subdichotomous, straight 

 and fastigiate, not or in the central portions very little anastomosing 

 branches somewhat resemble certain forms of L. tophiforme, although 

 they are thinner than frequently in this species, and it not unlikely 

 constitutes a separate and undescribed species. I am told that the 

 bottom was chiefly composed of Lithothamnia, but I have not got 

 full informations with reference to the conditions under which they 

 were tåken, and the extent of the layers. I, therefore, here do 

 not more nearly record the last named form. 



At some places along the Norwegian coast have been found 

 Lithothamnia above the present level of the sea, althoug not, so 

 far as I know, petrified forms. I have seen such at Tromso, but 



