MADEEPOEA. 155 



annular and immersed towards the base of the branch. The septa are very narrow, even in 

 the axial corallites ; in the radial ones usually only the directives are recognizable. Corallum 

 dense ; surface and wall closely echinulate. 



Var. mammillata. (Plate XXIII. fig. A.) 

 Two of the Rodriguez specimens consist of incrusting colonies in which the branches are 

 indicated only by conical protuberances, with very numerous and small immersed corallites 

 between. The protuberances are about 7 to 10 mm. high and, 6 to 11 mm. diameter, the 

 axial corallites 3'5 mm. diameter ; the radial ones crowded, scarcely prominent, with the walls 

 confluent. The larger specimen is 15 cm. long and 8 cm. broad. 



Rodriguez. 



a. Rodriguez. Royal Society [P.]. 76.5.5.103. (Type = il!f. ^/aw/a^iracc, Briigg.) 



Var. mammillata. 



i, c. Rodriguez. Royal Society [P.]. 76. 5. 5. 86 & 87. {=M.plantaginea,BTVigg.) 



E. Wall of the radial corallites rather thin and firm or slightly thickened, but not rounded 



at the margin. 



164. Madrepora australis. (Plate XXIII. fig. C.) 

 Madrepora australis, Brook, Ann. Mag. N. H. 1892, vol. x. p. 453. 



Corallum small cespitose, about 8 cm. high from a base 9 cm. in diameter. Branches 

 usually divided near the base into 2 or 3 erect digitiform branchlets, all of which reach to 

 about the same level, length 3"5 to 4*5 cm., diameter 2 to 2'5 cm. at the base, the distal 

 divisions 1"3 to 2 cm., angular below, slowly tapering to a blunt apex ; apices about 2"3 cm. 

 apart. Axial corallites 3 to 4 mm, diameter, hemispherical or a little tapering in the smaller 

 ones. Radial corallites rather distant and unequal, short, spreading, tubular, with more or 

 less oblique apex and plane margin ; aperture not compressed, diameter 1 to 2'5 mm., the 

 more prominent ones usually about 2 mm. diameter; length 1 to 2 mm., excepting near the 

 base of the branches, where a few are dilated and others more elongate and less spreading ; 

 the waU is a little thickened but not dilated, and the inner part is rarely entirely wanting. 

 A few subimmersed and immersed corallites are scattered between the more prominent 

 ones. Corallum moderately porous ; surface spongy and echinulate ; wall finely striate and 

 echinulate. 



A specimen, the habitat of which is not recorded, is referable to this species, but 

 differs in two or three points. The branches are more acuminate (axial corallites 3 mm. 

 diameter), and the radial corallites in many cases are gutter-shaped, owing to the imperfect 

 development of the inner part of the wall, and sometimes the lip is quite thin. It agrees, 

 however, with the type specimens in the mode of branching and in the spreading unequal 

 corallites, which are not compressed. The species is distinguished from M. guppyi by the 



