MADREPOEA. 171 



broad. Stems 2 cm. thick; branches and branchlets ascending, 2 to 10 cm. long and 8 to 12 

 mm. thick, proliferous and scarcely tapering except near the apex. Axial corallites 3 to 4 mm. 

 broad, 2 mm. exsert, margin a little rounded, aperture 1 mm. Radial corallites 1*5 to 2 mm. 

 broad, 3 to 4 mm. long, usually thin-walled, aperture round or oval, 1 to 1-5 mm. diameter ; 

 they are unequal, rather appressed half-tubular, with small subimmersed ones between; 

 others are completely tubular and bear buds ; below they are more appressed, or verruciform, 

 and finally immersed. Corallum moderately but not openly porous in section j surface spongy- 

 reticulate and echinulate ; wall striate. 



Several specimens are in the collection from the Persian Gulf which resemble M. variabilis 

 in habit, but have the thinner-walled tubo-nariform corallites of this species. One specimen 

 forms a corymbose clump 38 cm. in diameter. 



Indian Ocean : Red Sea, Persian Gulf. 



a-d. Persian Gulf. A. S. G. Jayakar, Esq. [P.]. 91. 1. 13. 5, 8, 22 & 31. 

 e. ? ? 93. 4. 7. 114. 



184. Uadrepora rousseaui. 



Madrepora rousseauii, M.-Edwards & Haime, CoraUiaires, t. iii. p. 138. 



Corallum small, shrubby arborescent, consisting of tufts of slightly tapering branches 

 up to 11 cm. in length; they are 1 cm. diameter from the base to within 3 cm. of the apex, 

 then tapering gradually to the axial corallite. Each branch bears numerous proliferations, 

 5 to 30 mm. long, which are prolonged and thickened tubular corallites bearing radial 

 corallites in proportion to their length. Axial corallites 2'5 mm. diameter (M.-Edwards 

 gives 3 mm.), 2 mm. exsert, with thick cylindrical wall. Radial corallites tubular or half- 

 tubular at an angle of about 45°, chiefly 2 mm. diameter and 2*5 mm. long, but many are 

 longer ; inner margin often incomplete, wall moderately thick, a little rounded at the margin j 

 those over 2'5 mm. long bear one or two small buds near the base, and thus lead on to more 

 marked proliferations and branchlets. A few immersed corallites are scattered between the 

 others, excepting near the apex of a branch and on the younger branchlets. Septa of the 

 axial corallites in one cycle only, subequal, moderately developed ; those of the radial 

 corallites also in one cycle, directives broad. Corallum dense ; surface a little pitted and 

 finely echinulate ; wall finely echinulate, excepting in the younger corallites, where it is 

 striato-reticulate or fenestrated. 



The above description is based on the types in the Paris Museum. A specimen in the 

 collection of the British Museum, which appears referable to this species, has the axial 

 corallites 2 mm. in diameter, the branches gradually tapering through their whole length, and 

 the shorter corallites nariform rather than tubular. 



Indian Ocean : Seychelles, Malacca. 



a. Malacca. Sir E. Belcher [P.]. 42. 11. 30. 18. 



