98 KJELLMAN, THE AhGM OF THE ARCTIC SEA. 



nearly that of L. soriferum and the species resembling it. It differs from L. glaciale, 

 besides in structure, even by the lesser thickness and more cylindrical shape of the 

 processes and by its tetrasporic sporangia. With L. soriferum or L. Ungeri it cannot 

 be confounded, the habit being different and the sporangia becoming grown over. The 

 name is meant to denote that in character it stands between L. glaciale and L. sori- 

 ferum and the species most closely allied to the latter. 



Habitat. The specimens I have collected myself, were taken in 5 — 10 fathoms 

 water on stony bottom, in a pretty well-sheltered locality. Here scattered individuals 

 were found. On the coast of Norway it has ripe tetrasporangia in the month of June. 



Geogr. Distr. It is known hitherto only from the Atlantic region of the Polar 

 Sea. The most northerly locality where it has been found, is KarlsO at Lat. N. 70°. 



Localities: The Norwegian Polar Sea: TromsO amt, for inst. at Troms5 (Foslie) 

 and Karls5; Finmarken, at Vadso (Foslie). 



Lithothamnion flavescens nob. 



L. fronde Crustacea, arete adnata; crusta tenuiore, vix 1 mm. crassa, e roseo flavescente, scabriuscula, 

 limbo laevi, subnitido, obsolete concentrice striato, margine subundulato, e cellulis majoribus formata; concepta- 

 culis sporocarpiferis et sporangiferis in eodem specimine sparsis, illis depresso-conicis, apice perforatis, his demum 

 innatis, creberrimis, magnis, diametro 700 /.i. heraisphaericis, prominentibus; sporangiis quaternas sporasfoventibus, 

 sporis maturis, 190—220 (/. longis, 50 — 100 fi. crassis. Tab. 6, fig. 1 — 7. 



Description of the species. Habit. The plant forms incrustations on other Litho- 

 thamnia, for inst. L. glaciale, L. compactum, and on shells of Balanidge. The crust is 

 closely adherent to the substratum, thin, scarcely one mm. thick, always uneven 

 when older, finely rugged and squamellate on the greater part of its surface. The 

 greater or smaller unevenness of the surface is caused by the substratum, to which it 

 clings closely. However the brim is smooth, feebly shining, Avith few indistinct con- 

 centric stripes; the edge is uneven, shallowly undulating. When younger the crust has 

 a faint rosy colour, which passes afterwards into faint brownish-yellow, which colour 

 increases when the plant dies, and appears particularly strong in the fracture (fig. 1). 



Structure of the frond. The lower co-axil system is feebly developed, its anticli- 

 nals converge gradually toward the matrix. In fragments of the frond, which have a 

 thickness of 0,3 mm., it takes up about 25 f^. The cells are elongated, about twice as 

 Jong as broad, rectangular or rhomboidical in radial section (fig. 3 — 4). In the upper 

 thickening-layer of the frond the cells, on a radial section, are four- angular, squarish 

 or rectangular, their longitudinal axis in the latter case running sometimes in the di- 

 rection of the radius, sometimes in that of the tangent. The outermost cells in par- 

 ticular are in the latter position. Their thickness amounts to 10—13 /u.- their length 

 does not exceed 15 ^. The cell-rooms are rounded, the walls about 2,5 /u. thick. The 

 surface cells are nearly isodiametrical in tangential direction, with rounded or rounded- 

 angular cell-rooms, 5—8 ,u. in diameter; the thickness of the dissepiment amounts to 

 4—5 ^. (fig. 5). 



