l;d. IV: 5) ANTARCTIC AND SUBANTARCTIC CORALMNACE^i. I3 



tlie nortliern and mucli varying Litliopli. incnistmis. This question, indeed, cannot 

 at present be settled \\ ith certainty. But at any rate Lithoph. icquabilc and A. 

 discoideiun are very nearly connected with each other. 



The species in question is distinguished from L. discoidcuiii particularly by tiie 

 inconsiderable thickness of the crust, 0.5 — !.■; mm., decreasing towards the edge, 

 ^\ hieb is almost ahvays considerably thinner than the central parts, and more or less 

 crenulate. The surface is partly rather smooth, partly a Httle uneven, particularly 

 on account of the fact that the roof of the conceptacles is often dissolved, and that 

 the filling up of the scars by new layers of tissue takes place somewhat irregularly. 

 At the same time, however, the crust shows a tendency to develop small ex- 

 crescences. This is a strong feature peculiarly in f. wandelica, in which are finally 

 developed a great number of small, irregulär excrescences somewhat confluent, in 

 much the same way as in feebly developed specimens of L. consociatitiii f. ty/>ica, 

 or even feebly plicate. In habit, this form also approaches young specimens of 

 Lithopli. falklandicitni. When growing older, f. zcaiidclica is easily detached from 

 the substratum, most likel)-, however, only b}' being attacked by animals, and in 

 certain circumstances new layers of tissue will be developed over parts of the side 

 turning downwards of the crust. 



In describing this alga, I observed that as to structure it approaches Arcliao- 

 lithothainnion, as in a section it partly shows numerous small squarish intermediate 

 cells, more or less oblique. Such cells were then known only in species o'i Arcliceo- 

 litliothaiiinion. Afterwards, however, I have found that these cells part!\' occur also 

 in Litlwph. discoideiun. Besides in a solitary case, I have seen similar ones in 

 PIiYuiatolithon {ClatlirouiPiphuiii) loculosuiii from the North Pacific. In the species 

 in question, the cells mentioned now occur, now are wanting, even in one and the 

 same section. Otherwise, the structure in all essentials corresponds with L. discoi- 

 deiun, though particularly in f. icandelica the cells are frequently a little broader 

 than they usually are in the said species. The cells of the hypothallium are 14 — 

 30 //, rarely up to 42 u long, and 6 — 11 u or mostly 7 — 9 ,» broad, the length 

 being 2 — 4 times or, exceptionalh-. up to 6 times the breadth. The perithallic cells 

 are 9 — 18 ,u long and 7 — 9 u or up to 11 u broad, the length being generali}' about 

 1V2 the breadth. Among these occur the small intermediate cells mentioned above. 



The conceptacles approach those of L. discoideum. When seen from above, 

 they are slightly depressed, 200 — 300 u in diameter. In a median-vertical section 

 they are roundish or roundish-flattened. The roof is often whoUy dissolved, but in 

 the thickest crusts overgrown conceptacles are yet found. I have seen no sporangia. 



The species is litoral on the coasts of Louis Philip Land and of South Georgia, 

 but at the South (Jrkneys it has been taken in a depth of 9 — 10 fathoms. Its 

 occurrence on the coasts of the Wandel Island is unknown to me. 



