160 



Meeresalg. t. III, fig. 7. However, it may even be confounded 

 with new local crusts in L. varians and other Lithothamnia much 

 attacked by animals, which are formed so as to cover the animals 

 or other objects and partly being free. It, on the other hand, 

 most •probabh/ is a well characterized species, but it wants doser 

 examination of larger fertile materials. 



Habitat. The plant occurs in the upper part of the sublitoral 

 region, descending to a depth of about 10 fathom, and appears to 

 prefer somewhat exposed localities. A specimen tåken in the middle 

 of June, fastened to L. tophiforme f. sguarrosa, was provided with 

 a couple of not well cleveloped conceptacles probably being those 

 of cystocarps. 



Occurrence. Found at Kjelmo in East-Finmarken, rare, ana 

 at Iyngo a little north off Tromso, rare. 



Litho thamn ion circumscriptum Stromf. 



Algveg. Isl. p. 20. 

 Descr. Lithothamnion circumscriptum Stromf. 1. c. 



Fig. „ „ „ „ t. 1, fig. 4—8; Fosl. Contrib. II, 



t. 3, fig, 8. 



Syn. Lithothamnion circumscriptum Fosl. Contrib. I p. 9, II,. p. 10. 



» » a areolatum Rosenv. Gronl. Havalg. p. 774. 



Bemark on the species and addition to the description. This 

 species is one of the most characteristic of the arctic crustaceous 

 Lithothamnia. It is most often easily recognized even in a sterile 

 stage. The frond attains a thickness of about 1 mm., frequently 

 however, about 0.6 — 0.8 mm. The limits between adjacent crusts 

 stumbling each other are always to be seen at ieast before the 

 plant bears sporangia a second time. Sometimes new crusts nere 

 and there are formed upon primary crusts stumbling each other, . 

 and, together with new formations effacing the scars after the 

 first developed sporangia, more or less efface the limits between 

 the primary crusts especially in richly sporangia-bearing specimens. 



The conceptacles of sporangia are very densely crowded and 

 occupy a sharply defined zone in the central portions of the frond, 

 developed from the centre towards the periphery, but a broader 



