106 M. FOSLIE ON THE LITHOTHAMNIA OF 
alternate, forming one row of short cells and two or four or sometimes up to seven rows 
of long ones. Also in Lithoph. craspedium the cells are alternately short and long, 
but the latter form only one or two, sometimes three, rows. The short cells in the 
species in question are subquadrate or vertically elongated, 9-14 u long and 7-11, 
broad, the long ones 18-22, sometimes up to 29 by 7-11 4. The perithallic cells are 
subquadrate, elongated vertically or horizontally, 7-11 p, or up to 14 p long in a vertical 
direction. Short groups of enlarged cells are frequently numerous. 
The alga appears to occur most abundantly in the Chagos Archipelago, but it is found 
well developed also at Coetivy. It bears reproductive organs in the months of May, 
June, and September, but old specimens are, as usual, almost always sterile. 
Localities. The Chagos Archipelago: Salomon Atoll, reef ; Egmont Atoll, reef and 
reef-edge ; Coetivy, E. reef. 
Area, The Maldives and Laccadives; and the Ellice Islands (Funafuti) in the 
Pacifie Ocean. 
13. LITHOPHYLLUM GARDINERI, Fosl., sp. n. 
Kgl. Norske Vidensk. Selsk. Skrift. 1906, n. 8 (1907), p. 30 (in Norwegian). 
Thallus forming masses partly and most frequently densely, partly somewhat spread- 
ingly branching, 3-5 em. high and 4—10 em. in diameter, attached at a younger stage by 
a crust-like hypothallus 1-3 mm. thick, at an older stage the hypothalius often almost 
disappearing; branches repeatedly subdichotomous, frequently rather anastomosing, 
sometimes forming in the basal part an almost solid mass, subfastigiate, terete or sub- 
compressed, short or somewhat elongated, straight or somewhat curved, knotty or here 
and there developing short side-branches, 2:5-4, seldom up to 5 mm. thick, feebly 
tapering and rounded, or the apices roundish-thickened ; conceptacles of sporangia 
convex, but little prominent, 240 (200)-360 & in diameter; sporangia four-parted, 
50-70 u long and 30—40 p broad (Pl. 15. figs. 1-4). : 
f. SUBREMISPHERICA, Fosl., f. n. | | 
Thallus almost hemispherical, about 15 em. high and 22-25 cm. in diameter; branches 
crowded and rather anastomosing, subfastigiate, short and rather curved, knotty, 
2-3 mm. thiek, with the apices rounded or subtruncate and sometimes depressed in 
the centre (Pl. 16). RR j 
f. OBPYRAMIDATA, Fosl., f. n. 
Thallus more or less obpyramidal, 4-6 cm. in diameter; branches frequently 
much anastomosing, subterete or compressed, with the apices roundish-thickened or 
subtruncate, often depressed in the centre, or irregularly dilated upwards and retuse 
(Pl. 15. figs. 5-8). : 
The typical form of this species, which I have named in honour of Mr. Stanley 
Gardiner, approaches in habit certain and particularly coarse forms of Lithoph. 
Kaiseri (cf. Pl. 15. figs. 1, 2, and Lithoth. in Mald. & Laccad. i. pl. 24. fig. 5). It 1s, 
