MADREPOEA. 115 



unequal in length, half-tubular or gutter-shaped, with a convex apex; length 1*5 to 2*2, 

 rarely 3 mm., diameter 1"5 mm. ; the wall is a little thickened, but very porous and strongly 

 tabulato-echinulate ; a few are thin- walled and scale-like. The angle of the radial corallites 

 varies from 40° to 80°, but is not usually over 60°. The septa are scarcely developed in the 

 prominent radial corallites, usually only the directive septa are recognizable ; in the immersed 

 ones the septa vary from this condition through a stage in which all the members of the 

 primary cycle are present with the outer directive most prominent, to one in which the six 

 primary septa are all moderately developed but equal. The surface of the corallum in the 

 older parts is closely vermiculate and echiuulate. 



The habitat of the type specimen is not recorded. 



a. ? ? 93. 4. 7. 90. (Type.) 



112. llladrepora elegantula. 



Madrepora elegantula, Ortmann, Zool. JB. 1889, Bd. iv. p. 507, pi. xii. fig. 5. 



Corallum irregularly cespitose, with divided and proliferous branches, tapering above. 

 The marginal branches are somewhat horizontal and flattened, with few corallites on the under 

 surface. Axial corallites cylindrical and thin-walled, 1'5 to 2 mm. diameter, frequently 3 to 

 5 mm. exsert ; the star may consist of 12 or only 6 septa ; the primaries are very broad and 

 nearly meet in the middle line. The radial corallites are chiefly appressed tubular, with the 

 inner part of the wall scarcely free when short, in other cases the shape is bursiform or nari- 

 form with a circular aperture 1 mm. or more in diameter ; length 4 to 8 mm., diameter 2 mm., 

 none are immersed except towards the base of the branches. Numerous tubular proliferous 

 corallites occur between the others, forming incipient branchlets. The star of the radial 

 corallites consists usually of twelve very narrow septa, the directives scarcely broader than the 

 others. Corallum porous ; surface vermiculate ; wall thin, openly striate and echinulate. 



The position of this species is uncertain, but it appears more closely related to M. afri- 

 cana than to any other species. 



Indian Ocean : Ceylon. 



a. Ceylon. Haeckel Coll. 92. 12. 5. 18. 



4. Subgenus LEPID0CYATHU8. 



Corallum usually corymbose or prostrate; in one species the colony is incrusting, 

 with low mammiform elevations in place of proper branches. The branches are terete and 

 usually scarcely tapering. Axial corallites similar to those of Polystachys ; they are pro- 

 vided with twelve septa ; the directives are usually slightly broader than the others. The radial 

 corallites are evenly distributed, scale-like, very spreading, giving a catkin-like appearance to 

 the branchlets. Sometimes there is a marked difference in size or angle between the 



