MADEEPORA. 



45 



Var. alveolata. (Plate XXVIII. fig. C.) 

 Corallum bushy, closely resembling the type, excepting that the radial corallites are 

 rarely completely tubular, they are usually nariform or half -tubular, sometimes with the 

 inner part of the wall slightly prominent. The prominent ones are more distant than in the 

 type, with smaller ones between. Usually only the directive septa are recognizable in the 

 radial corallites, the inner one often broader than the outer. 



Indo-Pacific Ocean : Keeling Island, China Sea, Torres Straits, Great-Barrier Reef. 



a. Keeling Island. 



Var. stricta. 



a-c. Tizard Bank, 3 fathoms. 



Var. alveolata. 



a-h. Rocky Island. 

 i. Thursday Island. 

 j. Palm Island. 



H. 0. Forbes, Esq. [P.]. 84. 2. 16. 1. (Type.) 



H.M.S. ' Rambler.' 89. 9. 24. 26. 94 & 95. {=M. 



cribripora, B.-Sm.) 



Saville-Kent Coll. 92 . 6. 8. 32 to 38 & 40. 

 Saville-Kent Coll. 92. 6. 8. 39. 

 Saville-Kent Coll. 92. 6. 8. 204. 



23. Madrepora nigra. (Plate XXVII. fig. C.) 



Madrepora ehrenbergii, B.-Smith {non M.-Edwards & Haime), Ann. Mag. N. H. 1890, vol. vi. p. 452. 

 Madrepora nigra. Brook, Ann. Mag. N. H. 1892, vol. x. p. 459. 



Corallum prostrate, openly reticulate; under surface subcomplanate, almost covered 

 with barnacle-growths ; corallites distant and very short, erect, tubular, rarely immersed ; 

 upper surface provided with erect or ascending branchlets arranged irregularly, not over 

 7 cm. long, and about 1*2 cm. thick near the base (including corallites), tapering to a slender 

 apex; apices about 3 cm. apart. Axial corallites cylindrical, 2 mm. diameter, 1 to 2 mm. 

 exsert. Radial corallites on the branchlets, tubular, with an oblique or gutter-shaped apex, 

 spreading almost at right angles, lower margin sometimes convex ; the corallites are usually 

 arranged in irregular rows, the majority are elongate and slightly compressed, 2 to 4 mm. 

 long and 1'5 to 2 mm. diameter, with a few subimmersed ones scattered between; the 

 margin is always sharply defined as if cut with a knife ; on the main divisions the corallites 

 are similar but not compressed, and the aperture is not so oblique ; the average length is 

 2 mm., and the diameter about the same. The star consists of two cycles of well-developed 

 septa, which extend their full breadth almost to the lip of the corallite, and therefore appear 

 especially well marked ; the directive septa are considerably broader and stouter than the 

 others. Corallum dense and stony ; surface linear echinulate and pitted, but frequently with a 

 spongy film over the surface ; wall distinctly striate, the strise become broken up into 

 echinulations near the base. The colour of the unbleached corallum is brownish black. 



Pacific Ocean : Tizard Bank. 

 a, b. Tizard Bank, China Sea, 5 fathoms. 



H.M.S. ' Rambler.' 89. 9. 24. 92 & 93. 

 (Types = Af. ehrenbergii, B.-Sm.) 



