42 M. FOSLIE. [1905 



As to the relation of the species to other ones, it may partly 

 be difficult to distinguish the form apiculata from a faintly deve- 

 loped L. nodulosum f. typica. On the other hand, f. dimorpha 

 in certain localities will in habit approach old specimens not typi- 

 cally developed of L. colliculosum, and is distinguishable only 

 by the parting of the sporangia. The species also approaches 

 L. nodulosum f. congregata, and in habit also L. grande, the 

 following species. It is, however, most nearly akin to L. tophi- 

 forme and L. soriferum, from which it is very difficult or almost 

 impossible to distinguish young nodules or slightly developed 

 spherical ones. In such specimens of L. fornicatum, however, 

 the branches are mostly thinner and more densely crowded than 

 in the said species, and the branch-systems are not distinctly 

 inverted pyramidshaped. On the other hand, small nodules are 

 considerably approaching a L. vardoense densely branching, which, 

 however, is mostly carrying smaller conceptacles, and the sporangia 

 are two-parted as in L. tophiforme. 



L. fornicatum occurs in the upper part of the sublitoral re- 

 gion from the lowest water mark to a depth of about 8 fathoms. 

 It prefers places sheltered, but generally only occurs where the 

 tidal waters are strongly running. In favourable localities f. ob- 

 crateriformis will attain a size of up to 0,5 m. in diameter, and 

 a weight of up to about 6 kilogrammes. The species almost al- 

 ways appears gregariousl} 7 in large numbers, partly associated with 

 other Lithothamnia, and often forms considerable banks. It occurs 

 in larger numbers than any other species on the coast of Norway. 

 The alga has been found with reproductive organs in January and 

 in June — September, but always only a few specimens among a 

 great lot of collected ones. In some places it has only been 

 found sterile. 



Area: Norway: From the north-eastern boundary to the 

 Trondhjem Fjord (!), Tusteren near Kristiansund N. (!)'), Vestnes in 

 Romsdal (Gran!), and in the neighbourhood of Bergen (Pali bin!) 2 ) 



!) All the specimens gathered in this place are sterile and somewhat appro- 

 aching L. colliculosum so as to make the determination uncertain. 



2 ) Two specimens I have seen from this place are feebly developed, 3 — 4 cm. 

 in diameter, but seem to have to be referred to this species. 



