MADREPORA. 125 
and gutter-shaped above, spreading at right angles, about 1°5 mm. broad and 1 mm. long; 
wall thin and fragile, except on some of the outer branchlets, where the corallites are more 
distant, of greater diameter, and have the wall considerably thickened and the margin 
rounded. Star rudimentary, often only the lower directive septum prominent. Corallum 
fragile ; surface rather dense, subreticulate, and echinulate, often in linear series; wall striate 
and echinulate near the base. 
The species occurs in shallow water in the neighbourhood of freshwater springs. 
Pacific Ocean : Carteret Harbour, New Iveland (Berlin Museum). 
124. Madrepora exigua. 
Madrepora exiqua, Dana, Zoophytes, p. 469, pl. xxxvili. fig. 2; Studer, MB. Akad. Wiss. Berlin, 1878, 
p. 533; Rathbun, Proc. U.S. Nat. Mus. 1887, vol. x. p. 15. 
Madrepora minima, Quelch, ‘ Challenger’ Reef Corals, p. 157, pl. ix. fig. 4. 
? Madrepora millepora, Quelch (non Ehrenberg), ‘ Challenger’ Reef Corals, p. 157. 
Corallum small, arborescent or subprostrate ; branches slender, 4 to 6 mm. thick, with 
a few short spreading branchlets 1 to 4 cm. long, slowly tapering to a relatively large axial 
corallite, sometimes arcuate, and with occasional fusions between the branches. Axial 
corallites 2°5 mm. diameter, 1 mm. exsert, or a little more, with a thick porous wall. 
Primary septa well developed, subequal, second cycle little developed or wanting. Radial 
corallites very small, unequal, 0°5 to 1 mm. diameter, the majority fragile and scarcely 
prominent, quite immersed on the older parts ; they are chiefly round-nariform, with a few 
of the more prominent ones labellate, 0 to 1 mm. long, aperture usually circular; directive 
septa well developed, the others narrow, second cycle absent or rudimentary. Corallum 
very porous ; surface finely reticulate and echinulate ; wall strongly striate, echinulate. 
Studer observes that the species grows on pieces of dead coral, near low-water mark. 
M. minima, Quelch, is subprostrate in habit, and the branches on coming in contact 
with a foreign body fuse witb it and form an incrustation over it; in all other respects it 
agrees closely with Dana’s description. 
Pacific Ocean : Fiji, New Hebrides, Solomon Islands. 
a, b. Api, New Hebrides. H.M.S. ‘Challenger.’ 86. 12. 9. 223, & 85.2.1. 15. 
(Types of M. exigua, Quelch.) 
?c. Api, New Hebrides. H.M.S. ‘ Challenger.’ 86. 12.9. 221. (=M.mille- 
pora, Quelch.) 
?d. ——? ——? 98. 4. 7. 120. 
125. Madrepora mirabilis. 
Madrepora mirabilis, Quelch, ‘ Challenger’ Reef Corals, p. 159, pl. x. fig. 5. 
Corallum prostrate ; branches originating laterally from a thick compressed elongate 
stem, and somewhat coalescent. Stem 4 cm. wide or more, tapering gradually. Under 
S 
