MADEEPOEA. 125 



and gutter- shaped abovCj 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 eorallites 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 Ireland {Berlin Museum). 



124. Madrepora exigua. 



Madrepora exigua, Dana, Zoophytes, p. 469, pi. xxxviii. fig. 2 ; Studer, MB. Akad. Wiss. Berlin, 1878, 



p. 533 ; Eathbun, Proc. U.S. Nat. Mus. 1887, vol. x. p. 15. 

 Madrepora minima, Quelch, ' Challenger ' Eeef Corals, p. 157, pi. 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 

 eorallites 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. Eadial 

 eorallites 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, 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 with 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. ? ? 93. 4. 7. 120. 



125. Madrepora mirabilis. 

 Madrepora mirabilis, Quelch, ' Challenger ' Reef Corals, p. 159, pi. 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 



