No. 3] REMARKS ON NORTHERN LITHOTHAMNIA. 93 



the former one. A specimen of Ph. loculosum I got from Mr. 

 K. Yen do, who had collected it at Shimushu, the northmost 

 of the Kurile Islands, forms a large flat piece, 1 — 2 cm. thick, 

 with even surface, and was hauled up, attached to the hold-fast 

 of Alaria fistidosa, from a depth of about 20 fathoms. New crusts 

 have been developed on the primary one which was partly dead 

 and apparently loosely attached to the substratum. This specimen 

 belongs to the tjrpical form of the species with numerous grown-in 

 conceptacles. Cp. Kjellman 1. c. Another specimen from the 

 said place encompasses a pebble and was found at the lowest tide 

 mark. The reefs were covered with the same species, which was, 

 however, here firmly attached to the substratum. The latter spe- 

 cimen represents a somewhat diverging form of the species, which 

 I propose to name: 



Phymatolithon (Clathromorphum) loculosum (Kjellm.) Fosl. mscr. 



f. evanida Fosl. mscr. 



The conceptacles of sporangia in this form are densely crowded, 

 resembling those in Ph. compactum f. circumscripta, but frequently 

 larger, in a median vertical section 300 — 500 /a in diameter. 



In Ph. loculosum the hypothallic layer is more vigorously 

 developed than in Ph. compactum and the cells are usually larger, 

 18—40 or up to 55 jj. long and 7 — 14 fi broad. The perithallic 

 cells are squarish, 7 — 11 fi in diameter, or vertically elongated, of 

 a length being P/2 — 3 times the breadth, being 7 — 20 or up to 

 26 p- long and up to 14 ft broad, not or seldom a little elongated 

 in horizontal direction of the frond. Thus the cells are frequently 

 larger than in the latter species, though specimens occur which in 

 this respect are hardly distinguishable. This is also the case as 

 to the conceptacles of sporangia. In Ph. loculosum too they are 

 visible after decortication as point-like or small cup-shaped holes 

 200 — 300 ft in diameter, the bottom of these holes forming a part 

 of the roof intersected with 10 — 20 muciferous canals. In f. ty- 

 pica only a part of the roof falls to decay after maturity, corre- 

 sponding with Ph. compactum f. typica, whereas in f. evanida 

 the conceptacles get fully dissolved as in f. circumscripta. The 

 sporangia usually are tetrasporic, occasionally only bisporic, 160 — 



