86 



by boring-muscles, which particularly destroy the lower part of 

 the crust, and always in very numerous passages made by worms. 

 It grows over younger individuals of Mytilus, shells of Balanidas, 

 tubes of Serpula and numerous other animals fastened to or living 

 on it. It also serves as a substratum for Maria, Laminaria and 

 other algae, often widely extending over the rocks, and, not seldom, 

 growing over the root and the lowest part of the stem of those 

 large algae. Specimens bearing conceptacles of sporangia have been 

 taken in June, July, August and September, but in very small 

 numbers and few of them containing sporangia. A solitary speci- 

 men collected in the later half of September was, as above men- 

 tioned, provided with some few conceptacles of cystocarps and 

 probably also antheridia. 



Occurrence. I here only record the localities from which I 

 have specimens left, viz, Havningberg and Berlevaag in East- 

 Finmarken, Honningsvaag, Havosund, Gjesvaer and Ingo in West- 

 Finmarken. A specimen from Kjelvik, picked up from a depth of 

 about 15 fathom, perhaps also belongs to the same species. Besides 

 it has been gathered at Skorpen in Kvasnangen, and at Balstad 

 and Borgevaer in Lofoten. 



Geogr. Distribution. Some specimens from Greenland that I 

 have seen, determined by Kj ell man as L. polymorphum, not 

 unlikely, at least in part, belong to this species. Cp. Kjellm. 1. c. 



Lithothamnion polymorphum (L.) Aresch. 

 in J. Ag. Spec. Alg. 2, p. 524; Millepora polymorpha L. Syst. Nat. p. 1285; 

 ex parte. 



Descr. Lithothamnion polymorphum Stromf. Algveg. Isl. p. 19, t. 1, fig. 1 — 3. 

 Exsicc. „ „ Aresch. Alg. Scand. exsicc. No. 302. 



f. tuberculata Fosl. mscr. 



f. crusta tenuiore; tuberculis 2- 3 mm. altis, 2 — 5 mm. crassis, 

 obtusis vel truncatis plus minusve dense dispositis. Tab 17, fig. 

 17—19. 



f. valida Fosl. mscr. 



f. crusta crassiore; tuberculis fere hemisphaericis, diametro 

 5—20 mm., altitudine 2—6 mm. Tab. 17, fig. 20—21. 



