MADREPORA. 83 
72. Madrepora tenuis. 
Madrepora tenuis, Dana, Zoophytes, p. 451 ; M.-Edwards and Haime, Coralliaires, t. iii. p. 152; Quelch, 
‘Challenger’ Reef-Corals, p. 157; Rathbun, Proc. U.S. Nat. Mus. 1887, vol. x. p. 19 (non 
Ortmann, Zool. JB. 1888, Bd. iii. p. 152; ? B.-Smith, Ann. Mag. N. H. 1890, vol. vi. p. 453). 
Corallum cespitose, rounded, sparingly spreading; branchlets very slender, scarcely 
4 mm. thick, 7-5 cm. long, subterete and proliferous. Axial corallites 1-3 mm. broad, a little 
prominent. Radial corallites appressed, tubiform, irregular, about 1:3 mm. broad and 3 mm. 
long, attached not quite to the summits; margin fragile, aperture circular; exterior neatly 
striate and finely scabrous ; star indistinct, the directive septa a little prominent. (Dana.) 
The specimens from Samboangan referred by Quelch to this species agree fairly well 
with the above description. The habit recalls that of M. rosacea, Esp., but the branches are 
rather stouter and more divided, and the corallites much shorter, with broadly striate wall. 
Axial corallites cylindrical, 1-5 mm. diameter, with thin wall, a little exsert. Radial corallites 
ascending tubular, with thin wall and circular aperture; a little unequal in length and 
diameter, some bear buds: diameter 1 to 15 mm. and 2 to 35 mm. long, becoming shorter 
and more irregular below. Star moderately prominent, composed usually of six delicate septa 
of which the directives are the broadest. Corallum very porous; surface and wall striato- 
echinulate. 
Kast Indies, Samboangan, ? Tizard Bank, Great-Barrier Reef. 
a-c. Samboangan. H.M.S. ‘Challenger.’ 86, 12. 9. 242 & 411; 92. 10. 
16. 31. 
d. Wreck Bay, Great-Barrier Reef. J.B. Jukes, Esq. [P.]. 46. 7. 30. 9. (Young colony.) 
?e. Tizard Bank. H.M.S. ‘Rambler.’ 89. 9. 24.96. (=WM. tenuis ?, 
B.-Sm.) 
73. Madrepora africana. (Plate XXXV. fig. B.) 
Corallum small, cespitose, resembling M. tudbicinaria in habit ; height 5:5 cm., diameter 
9 or 10 cm. Branches simple or divided near the base and irregular in outline, owing to 
inequalities in the size of the radial corallites ; length 3 to 3°5 em., diameter 7 mm. near the _ 
base, but more near the apex owing to the presence of stout, prominent, and often proliferous 
corallites in that position. Axial corallites cylindrical, little prominent, 3 to 3°5 mm. 
diameter, aperture 1°5 mm., wall very porous; septa moderately developed, the primaries 
equal, the second cycle very narrow. Radial corallites appressed nariform to tubiform, 
rather small and crowded near the apex, but becoming more distant and of much larger 
diameter a little lower down; length 2 to 5 or even 6 mm., diameter 1°3 to 2°5 mm. 
Towards the base of the branchlets one or more elongate ascending tubular corallites occur, 
which may be 10 mm. long and 3 mm. diameter, with or without a few small buds. The wall 
of the radial corallites is usually quite thin and even in the long tubular corallites is not over 
0°5 mm. thick. The arrangement of the radial corallites is very irregular, and on the basal 
parts most are immersed or subimmersed. In the prominent corallites usually only the 
directive septa are recognizable, and the outer one is usually broader than the other. In the 
