I 2 



1,\ about 40 delicate muciferous canals. The root' finally falls off, and dissolved conceptacles only 

 leave smal! elevated edges, or a scar more or les distinguishable. The four-parted sporangia are 

 60 — 70 ■>.. long, and 25—30 ;j.. broad. The conceptacles of cystocarps are almost superficial, 

 conical, sometimes however rather low, abruptly passing into a very short and thin tip, which 

 soon falls away, 550 450 ■>.. in diameter, when seen from above. Antheridia are unknown. 



The typical form of the species in sterile stage is easily confounded with young Squa- 

 mariaceae, and is sometimes hardly distinguishable from young specimens of Lithothamnion 

 simulans. The form pseudoramosa is in habit approaching young and stunted specimens ot 

 Lithothamnioti fruticulosum f. clavulata, for which it is easily mistaken, sometimes being hardly 

 distinguishable from it also as to structure. It is of no infrequent occurrence that it covers 

 specimens apparently belonging to the form mentioned. 



Specimens of the present species having been collected in April, May, July and December 

 are sparingly provided with cystocarps and sporangia. In the Gulf of Siam the species bears 

 these organs in the month of February. 



Occurrence: On the whole this species occurs rather scarcely. The comparatively greatest 

 number has been found at the stations 49 a , 64, 258. The species mostly has been found associated 

 with Lithothamnion fruticulosum and Lithothamnion australe^ but almost always it shares the 

 substratum also with stunted specimens of other calcareous algae and a series of lower animals. 



Area: Xorth Pacific: The Gulf of Siam. 



2. Litliothamnion bandanum Fosl. mscr. Fig. 4; PI. I, fig. 10. 



Thallus crustlike, up to 0,5 mm. thick, closely clinging to the substratum. Conceptacles 

 of sporangia subprominent, 250 — 450 u.. in diameter. 



Stat. 240. Banda. Lithothamnion bank in 18 — 36 m. 



Of this species only a single specimen is known. It is 1 cm. in diameter, and forms 

 a crust, up to about 0,5 cm. thick round the substratum, whose form it assumes. Some 

 wartlike excrescences seem only to be owing to the form of the substratum, and it is 

 questionable whether such ones really are developed from the crust at all (PI. I, fig. 10). 



A vertical section exhibits a faintly developed hypo- 

 thallium, formed by rows of cells whose lower anticlines are 

 but very sligthly converging to the substratum. The cells 

 attain a length of 12 — 20 a., and a breadth of up to 10 a. — 

 The cells of the perithallium are rather irrecnilar and have 



rig. 4. Lithothamnton bajiaanum frosl. 1 ö 



Part of tiie perithallium in vertical section, with often thick walls. The\' are partly roundish, partlv (and 



transversaly cul feeble hypothallic layer , . ,, , , 



;j mostly) vertically elongated, 7—15 or sometimes up to i8p. 



long, and 6 — 8 or seldom up to ioix. broad. There is no 

 distinct stratification to be seen in a section, but new hypothallic layers here and there are 

 formed over conceptacles or small extraneous objects (Fig. 4). 



The conceptacles of sporangia are at first convex, partly very slightly rising above the 

 surface of the thallus, partly subprominent, finally fairly flattened, rather crowded in any part 



