8 M. FOSLIE. [1899 



The plant is perhaps attached at first to some hard object, 

 but afterwards detasches itself and lies free on. the bottom. The 

 thallus has a short, either flattened and upwards broadening, or 

 extremely short and almost terete mainstem, from which there issue 

 repeatedly subflabellate or irregular branchsystems spreading almost 

 in one plane, the one over the other. The more or less compressed 

 branches are about 1.5 mm. thick, and frequently much confluent 

 with each other. The tips of the branches partly are rounded 

 partly almost truncate. The solitary apparently endre specimen that 

 I have seen is 7.5 by 5.5 cm. in diameter and about 2 cm. thick. 



The conceptacles of sporangia are scattered or somewhat 

 crowded, but upon the whole very scarce in the specimens exa- 

 mined, subprominent, seen from above 350—400 p. in diameter, 

 flattened in the central parts, or almost disk-shaped, though some- 

 times not sharply defined. The roof is intersected with about 30 

 coarse muciferous canals. Sporangia not known. 



A longitudinal section of a branch shows indistinct stratified 

 tissue, the cells nearly always longer than broad, with thick walls,, 

 according to a solitary section 10 — 18 /x long and 7 — 12 /x broad. 



The only locality known is Prospeetee Harbour, off Tahiti,. 

 20 fathoms. Cp. the locality above stated. 



Lithotham nion superpositum Fosl. mscr. 



Thallus forming irregular crusts growing over each other,. 

 sending forth short, simple or irregularly divided, knotty branches- 

 about 2 mm. thick. Conceptacles of sporangia rather crowded in 

 the branches, subprominent, 400 — 500 /^ in diameter, depressed in. 

 the central parts. 



I have seen but a solitary specimen of this characteristic spe- 

 cies, the longest diameter at the base being about 2,5 cm. and of 

 about the same height. It has been fastened to the rock or any 

 hard object, at first forming irregular crusts growing over each 

 other, in part also over a small tuft of Corallina, and especially 

 in the central parts rising to a height of about 1 cm,., forming 

 irregular cup-shaped layers of knotty crusts here and there sending 

 forth short branches, but from the central part of the last developed' 



