130 



solitary and fragmentous specimen of an alga, which I supposed 

 to be referable to LithopliyUum and considered nearly connected 

 with L. arcticum (Kjellm.) 1 ), a species showing close affinity to 

 L. lichenoides. It in fact belongs to Eulitliotliamnion. Young 

 specimens certainly rather remind one of younger specimens of 

 that species, but older, which I have later collected, are quite dif- 

 ferent and really most closely related to certain forms of L. fla- 

 vescens. However, with reference to structure it sometimes nearly 

 approaches the subgenus LithopliyUum. 



The plant forms incrustations on other Lithothamnia, partly 

 dead specimens, as L. glaciate, L. fruticulosum and L. tophiforme. 

 Young individuals are nearly orbicular (pi. 22, fig. 2), older ones 

 of irregular shape and rather extended. The frond clings more 

 or less closely to the substratum; more closely to little or coarse- 

 branched hosts as certain forms of L. glaciate, but is frequently 

 onty here and there adherent, more free in a host with much 

 spreading branches as L. tophiforme f. squarrosa, or stretched 

 over the branches of densely branched specimens of L. fruticulo- 

 sum (pi. 22, fig. 5), however, it also closely clings over and be- 

 tween the upper branches, though frequently even then but here 

 and there attached. The peripherical portion or sometimes even 

 a larger part of the crust partly and most frequently is quite free, 

 undulate-lobate, bent a little upwards or irregularly bent, partly, 

 however, attached to the substratum, though not closely. The 

 upper side of this portion is most often rather feebly concentric 

 zonated or in thin crusts provided with subconcentric furrows, 

 which also occur in the lower part, but here narrower and more 

 sharply defined, or in the latter part it even forms small ridges. 

 PI. 22, fig. 3 — 4. Sometimes the upwards turned part of a free 

 peripherical portion is in thicker crusts nearly smooth or not zona- 

 ted, but the lower part either concentric zonated or provided with 

 small ridges. Now and then the crust puts forth a peripherical, 

 free, disc-like or somewhat convex-concave and nearly reniform 

 lobe. It is frequently feebly shining, older specimens with a more 

 or less uneven surface, finely rugged and squamellate, or often. 

 *) Kariska hafvets Algveg. p. 16. 



