66 M. FOSLIE. [1905 



f. uncinata Fosl. 



Rev. Syst. Surv. Melob. p. 13; Lithothamnion uncinatum Fosl. Norw. Lithoth. 

 (1895), p. 126, t. 19, fig. 11-14. 



f. similis Fosl. mscr. 



Frond simple or subsimple, curved, 1 — 1,5 mm. thick. 



Syn: Lithothamnion norvegicum Fosl. List of Lithoth. (1898), p. 6, Rev. Syst. 

 Surv. Melob. p. 13; De Toni, Syll. Alg. IV (1905), p. 1742. 



This species is almost always freely developed on the bottom, 

 sometimes, however, attached to pebbles, and then developing a 

 feeble crust, but afterwards frequently detached. The form pusilla 

 is perhaps the typical form of the species. It mostly varies be- 

 tween 1 and 3 cm. in diameter, the branches are partly crowded, 

 partly sparingly divided, and more or less diverging. It runs into 

 f. uncinata, which is a little coarser and becomes up to 6 cm. in 

 diameter. The specimen of f. uncinata pictured 1. c. is not a 

 typical one, as it has partly — and peculiarly in the lower part 

 — been worn by friction. The parts worn have then been partly 

 covered with a thin crust, here and there growing over and cove- 

 ring up small extraneous objects. These parts, therefore, are thicker, 

 and the branches in consequence are more attenuating than usual 

 in this form. Besides the specimen bears more lateral branches 

 than specimens typically developed, though the form is frequently 

 more densely branching than the said specimen. The form similis 

 is in habit wholly resembling L. calcareum f. subsimplex, but is 

 more delicate. It runs into f. pusilla. All the three forms, ho- 

 wever, are little independent, as numerous transitions are found. 

 Still there is a considerable difference between a f. uncinata vigo- 

 rously developed and a delicate f. pusilla or particularly a simple 

 f. similis. Therefore I think that they ought to be admitted as 

 denominated forms. 



The conceptacles of sporangia resemble those of L. nodulosum. 

 They are scattered or crowded in the upper part of the branches, 

 300— 400 p. in diameter. The sporangia are tetrasporic, 90 — 130/-* 

 long and 25—45 p. broad. The said conceptacles, when emptied, 

 are usually quite dissolved. The cystocarpic ones are conical and 

 of about the same diameter as those of sporangia. 



