54 MADREPORARIA. 
Form A. florida. 
Corallum erect, arborescent ; main branches spreading, but their subdivisions are little 
divergent ; branches thick and elongate (25 cm.), scarcely tapering, 3°5 cm. diameter near 
the base and 3 cm. up to within 3 or 4.cm. of the apex. Rosettes about 1 em. high and 7 mm. 
broad, but a few are considerably larger. Axial corallites 2 mm. diameter, sometimes 3 mm. 
exsert, often a little compressed ; aperture round or slightly oval; wall firm but not specially 
thickened. The central corallites of the rosettes have the same dimensions, but the aperture is 
more or less oblique ; usually the aperture is oval, with a notch in the wall at one or both 
extremities. Radial corallites of the rosettes spreading, sometimes nariform, more usually 
half-tubiform or labellate, of variable length up to 2°5 mm. or even more ; lip 1°3 mm. broad. 
Between the rosettes the corallites are nariform, labellate, or immersed, the immersed form 
increasing in number some distance below the apex. The apex of a branch often shows the 
formation of the rosettes. At first a few radial corallites become elongate and thicker (4 mm. 
long and 1°6 mm. thick), with or without one or two radial buds; those between are labellate 
or nariform, not over 1 mm. diameter and 2°5 mm. long. Corallum very porous, but becoming 
dense below; surface dense and echinulate; wall closely striate, the striz more or less 
echinulate. The star consists of 6 narrow septa in the axial corallites,in the radial ones 
usually only the directives are noticeable. 
A specimen from Malacca, which I take to represent an earlier condition of this form, 
differs in the almost complete absence of proliferations worthy of the name “rosette,” and in 
consequence the branches are not so thick, scarcely over 2m. The condition of the surface 
of the whole specimen, which is 32 em. high, is very similar to that of the apical 3 or 4 em. 
of a branch in the more typical form. The stouter corallites are frequently not yet proliferous, 
and at most bear 3 or 4: short buds. 
Form B. confluens. 
? Madrepora horrida, B.-Smith, Ann. Mag. N. H. 1890, vol. vi. p. 452. 
Corallum forming a frond composed of confluent branches. Base oval, 10°5 by 6 cm.; 
branches 2 to 3 em. thick, about 30 em. long, chiefly in one plane, the subdivisions frequently 
arched. The upper surface bears a large number of rosettes, from 5 to 15 mm, high, but 
chiefly about 8 mm. The interval between the rosettes as in form A, excepting that some of 
the labellate corallites are more elongate. Under surface without rosettes or very prominent 
corallites ; they are chiefly suberect nariform, short tubular or labellate, with immersed ones 
scattered between. Corallum extremely porous ; surface reticulate above, becoming firmer 
below, echinulate; wall finely striate, echinulate. 
A number of other massive specimens in the Collection are probably referable to this 
variety, and the specimens referred to M. horrida by Bassett-Smith appear to me to be an 
incrusting form in which the rosettes are not well marked. 
Pacific Ocean : Fiji, Tongatabu, Louisiade Archipelago, Malacca, ? Tizard Bank. 
