[S 



defined. Antheridia are not yet known with certainty, and as regards the sporangia I refer to 

 remarks under G. myriocarpon. 



< Iccurrence: Also this species appears to be rather widely dispersed, but it apparently 

 never occurs in any great number at the stations above quoted. 



Area: Indic : The Maldives and Laccadives; the Red Sea; Zanzibar. 



3. Goniolithon megalocystum Fosl. mscr. Fig. 20 ; PI. IX, fig. 8 — 9. 



Thallus crustlike, convex-concave, 0,3 — 0,5 mm. thick. Conceptacles of sporangia sub- 

 lical, Iow, [,5 — 2 mm. in diameter. 



Stat. 93. Pulu Sanguisiapo, Tawi-Tawi Islands, Sulu Archipelago. 12 m. Lithothamnion bottom. 

 Stat. 129. Kawio and Kamboling Islands. Karkaralong-group. Reef. 



There is known but a solitary typical specimen of this species. It is fragmentary, towards 

 4 cm. long by a breadth of about 2 cm. There is 110 evidence that is has been attached, but 

 it forms only a part of a larger specimen which probably has been fastened to some hard 

 object. The crust is -convex-concave and approaches in shape one half of the shell of a muscle 

 (PI. IX. fig. 8). It is about 0,5 mm. thick in the thickest part, plainly decreasing towards the 

 margin which is 0,2 — 0.3 mm. thick and somewhat rounded off. In the upwards turning part 

 the crust is provided with rather faintly distinctive, concentric ridges, and in the lower part it 

 is concentric striate or shallowly furrowed. 



A radial section of the crust exhibits a vigorous hypothallium. The central cells of this 



layer are 25 — 35, here and there up to about 40 u.. long, 

 and 10 — iS u. broad, with rather thick walls. It sends forth 

 perithallic rows upwards and downwards, which however are 

 very feeble in the thinner parts of the crust (Fig. 20 A). 

 The upper layer increases in thickness towards the thickest 

 part, where it shows an extent of about 200 u.. The cells 

 of this layer are partly squarish, partly vertically elongated, 

 about 10 'j.. in diameter, or up to about 18 u. long. A 

 few heterocysts occur. 



The plant bears a few conceptacles of sporangia in 



the month of July. They are conical, but low, rather abruptly 



passing into a short and thick tip, not distinctly defined, 



r,5 — 2 mm. in diameter, when seen from the surface. The 



sporangia are thinly scattered over the almost plain bottom, 



100 — 140 u. long and about 60 u.. broad. 



With some reservation I refer a couple of somewhat differing specimens to the same 



species. They not unlikely represent a form corresponding with similar forms of Lithothamnion 



fragilissimum and L. simulans. The crust is about 0,3 mm. thick, loosely covering Bryozoa, 



Squamariaceae, a young Goniolithon frutescens and other calcareous algae attached to a coral 



alocystum Fosl. 

 .1. Radial section of the type specimen: 

 B. Vertical section of the form pictured 

 pi. IX. fig. 9: 72. 



