of the crust, 250 — 450 u.. in diameter, when seen from above. Two or three conceptacles 

 sometimes become confluent. The roof is intersected with about 30 muciferous canals. The 

 conceptacles become overgrown and appear in great number in a section of the crust. A few 

 ones examined were partly emptied, partly attacked by animals who had destroyed the sporangia. 

 The specimen was picked up towards the end of November, therefore the plant is likely to 

 bear mature sporangia by this time. 



In habit this species on one hand approaches a little certain forms of Lithothamnion 

 Engelhartii, and on the other hand L. fumigatum. It is however most closely allied to L. 

 maldivicum both in habit and structure, but the conceptacles are much smaller, and as regards 

 structure it mostly shows smaller and less thick-walled cells than the said species. 



Occurrence: The only specimen met with was found among a number of stunted 

 calcareous algae from the quoted station apparently belonging to Lithothamnion fruticulosum , 



6. Subramosa. 



3. Lithothamnion fragilissimum Fosl. mscr. Fig. 5; PI. I, fig. 11 — 16. 



Thallus crustlike or more or less leaf-like, 150 — 500 fjt. thick, horizontally extended, 

 partly attached, scantily and irregularly prolificating. Conceptacles of sporangia convex, but 

 very little prominent, at length somewhat flattened, crowded, 350 — 450 u. in diameter. 



Stat. yS. Lumu-Lumu-shoal, Borneo-bank. 

 Stat. 81. Pulu Sebangkatan, Borneo-bank. 

 Stat. 234. Nalahia Bay, Nusa-Laut Island. Reef. 



The plant occurs partly, and particularly when young, clinging rather closely to the 

 substratum, partly, and most frequently, but loosely covering the latter, here and there attached 

 to it. At lenght the greater part of the thallus gets free. It is 150 — 500 u.. thick, decreasing 

 in thickness towards the margin, somewhat shining, rather 

 brittle, but on the other hand of a rather hard consistencv. 

 Judging from a solitary almost entire specimen it is some- 

 what lobed (PI. I, fig. 1 1). The species is scantily prolifica- 

 ting. The prolifications partly more or less cling to the 

 primary crust, partly they are semi-circular and somewhat 

 rising, or irregularly plicate, mainly when covering up 

 extraneous objects. Besides it is often provided with small 

 and irreeular excrescences, which also are due to its 

 covering up different objects. The plant is concentric zonate, 

 distinctly so in the part turning downwards, in the part 

 turning upwards indistinctly. 



As to the Structure, a radial section of the crust * ? 2 ' ?• ^rt of the perithaUic fcyer in vertical section; 



X 390. C. Radial section near the margin; X 72. 



shows a marked and rather vigorous coaxial hypothallium, 



which in the central parts of the crust frequently sends forth upwards rather long perithallic rows. 



On the contrary, in the peripherical portions the perithallium is very faint (Fig. 5 C). The 



EoaaaGL 

 DaOODDOC 



DaaaoDoc 



Doaaooac 



DCDOOOOcoc 

 DO CO 30g<2C 



-ir— ii — 11 — inn nr 



Fig. 5. Lithoth fragilissimum Fosl. 



./. Vertical section towards the central part of the crust; 



