THE PERCY SLADEN TRUST EXPEDITION. 99 
Conceptacles of cystocarps do not occur. The specimen in structure also mainly 
resembles Lithothamnion purpurascens, forming feebly-marked layers of tissue. It has 
been dredged at a depth of 45-60 fathoms together with a couple of stunted pieces of 
another calcareous alga and a crust-like Foraminifer. 
Locality. Indian Ocean: the Amirante Bank, No. E 27 (Stanley Gardiner). 
Area. The Gulf of Siam. 
2. LITHOTHAMNION INDICUM, Fosl. 
Kgl. Norske Vidensk. Selsk. Skrift. 1906, n. 8 (1907), p. 7 (in Norwegian). 
Resembles Lithoth. fruticulosum f. erassiuscula, but the bottom of the conceptacles of 
sporangia almost plane or feebly convex according to the shape of the layers of tissue, 
and particularly the lower corners in a median-vertical section often not or but feebly 
rounded ; conceptacles of eystocarps almost superficial, conical. 
f. TYPICA. 
Syn. Lithothamnion fruticulosum f. crassiuscula, Fosl. Lithoth. Mald. & Laccad. in Gardiner, Fauna 
and Geogr. of the Mald. & Laccad. Archip. i. p. 464, pl. 24. figs. 2, 3; Lithoth. Adriat. Meer. 
in Wissensch. Meeresuntersuch. vii. (1905) Helgoland, t. f. 1. figs. 7-9; Lithoth. in ‘ Siboga" 
Exp. n. lxi. livr. 18, p. 19, pl. 2. figs. 1-4. 
f. suBTILIS, Fosl. 
dh C: 
Shape and size of the branches corresponding to Lithoth. fruticulosum f. clavulata. 
Syn. Lithothamnion fruticulosum f. clavulata, Fosl. Corall. in Fl. Koh Chang, in Bot. Tidsskr. xxiv. 
(1901) p. 17 ; Lithoth. Adriat. Meer. l.c. t. 1. figs. 16-17; Lithoth. in ‘ Siboga’ Exp. l. c. pl. 2. 
figs. 5—9. 
This ks has previously been referred to Lithoth. fruticulosum, which it resembles both 
in habit and as to the form and size of the conceptacles of sporangia,—apart, however, 
from the fact that these organs, as I have earlier observed, in Lithoth. indicum for 
the most part show a more even bottom with sharper corners than usual in Lithoth. 
Jruticulosum. This is not, however, a well-defined character, as typical Lithoth. fruticu- 
losum shows sometimes the same state of things as to these organs, and, on the other 
hand, specimens of Lithoth. indicum occur, especially feebly developed ones, in which 
the conceptacles in a median-vertical section now and then show nearly the same 
form as in Lithoth. fruticulosum. As to the cystocarpic conceptacles, I remarked in 
Lithoth. Mald. & Laccad. l.c., that the only point of difference from Lithoth. fruticu- 
losum “ appears to be the fact that the conceptacles of erystocarps are more acute than 
generally seen in specimens from the region last named " (the Mediterranean and the 
Adriatic). The specimens in which these organs were found corresponded, however, 
With a rather delicate and not well developed f. clavulata, Therefore I could attach no 
special importance to this character. In ‘Siboga’ Exp. n. lxi. p. 22, I also mentioned a form 
in which I found a few cystocarpic conceptacles which proved a little diverging from 
those of typical Lithoth. fruticulosum. But these specimens also were not well developed, 
in part even quite stunted and bearing only one or two of the organs in question. I have 
not till quite recently succeeded in finding them well developed and occurring in some 
