38 



Tromsø Museums Aarshefter. 14. 1891. 



ded corners, 9 — 17 \k high and 5 — 9 [x thick. I have not 

 found any certain overgrown conceptacle of sporangia. How- 

 ever, the hypothallus and lower part of the branches espe- 

 cially, but also the upper part of the branches is traversed 

 with numerous, wider or finer passages made by worms, 

 and it may be that some of the cavities seen on a trans- 

 verse or longitudinal section of a branch really are over- 

 grown conceptacles, although they look more like passages 

 of worms. 



The specimen is steril. It was tåken in the spring or 

 the earlier half of the summer. 



Lithothamnion fornicatum nob. 



L fronde initio circum conchas vel lapidea effusam, demum libe- 

 ra, fornieata, diametro usque 40 cm., crassitudine 1 — 2 cm., decompo- 



sito subdichotome ramosa ; ramis teretibus, pius minas coalitts, apici- 

 bus obtusis vel sæpe rotundatis, ramulis brevissirnis, plerumque verru- 

 cæformibus sæpe præditis ; conceptaculis sporaugiferis nunquam inna- 

 tts. Tab. 1—2. 



In a younger state the plant forms a rather thin crust 

 especialfy on muscles but sometimes also on stones, with 

 short, simple or subsimple processes, very much resembling 

 a younger L. glaciale or L. intermedium. Afterwards it com- 

 pletely surrounds the object 1 , the crust furthermore being 

 thin but densely furnished with short and subdichotomous 

 branches, with axes of at least two orders. The branchsy- 

 steras always anastomose below, by serveral specimens near- 

 ly to the tip of the branches, and are not seldom almost 

 impossible to follow. The branches are terete or nearly 

 terete, erect, fastigiate, straight and obtn.se, or slightly ta- 

 pering with small wart like processes, and sometimes bea- 

 ring short subcylindrical ramelli until 3 mm. long. Speci- 



i 



In the locality where I met with this spedes, a number of living 

 muscles (Mytilus modiolus) were more or lets «urrounded by the 

 plant, xtmj of tliem dying. 





j 



) 



