MADREPOEA. 95 



52 cm. broad and 10 to 14 cm. high. Under surface complanate; branches crowded and 

 coalescent, somewhat flattened below ; branches 1 cm. thick, with numerous much appressed 

 corallites and a few tubular ones, which are lateral in position and give rise to branchlets 

 in the general plane; some are simple, 8 to 10 mm. long and 2 mm. thick, others bear lateral 

 nariform corallites, others, again, tubular ones, those near the base being elongate and very 

 spreading; immersed corallites almost absent from the under surface. On the upper surface 

 the main branches give rise at intervals to clusters of two to five suberect branchlets ; the 

 more central ones are erect and simple or forked, 5 cm. long and 6 mm. thick at the 

 base, distinctly tapering; nearer the margin of the colony the branchlets are oblique and 

 arcuate and bear clusters of 2 to 5 short twigs which are 1 to 2 cm. long and 4 mm. thick ; 

 apices 6 to 9 mm. apart. Upper surface of the main branches and base of the branchlets 

 provided with numerous large immersed corallites, with an aperture of 1 mm. Axial coral- 

 lites about 2 mm. diameter, usually about 1 mm. exsert. Radial corallites ascending, 

 elongate, labellate, and imbricate, 3 to 4 mm. long and 1"5 mm. thick; apices more or less 

 pointed. Corallum very porous and reticulate in section ; surface densely echinulate ; wall 

 thin, finely striato-reticulate and echinulate, except in the case of the younger ones. Star 

 not recognizable in the prominent corallites or only the directive septa present; in the 

 immersed ones it sometimes consists of six very narrow septa. Two specimens have the apices 

 of some of the twigs subdivided ; in the third the majority are proliferous. 



Mauritius. 



a. Mauritius. Purchased. 78. 2. 4. 9. ■» 



b, c. ? Purchased. 49. 1. 4. 1 & 2. J ^P^^* 



86. Madrepora pectinata. (Plate XXVII. figs. D, E.) 



Madrepora peetinata, Brook, Ann. Mag. N. H. 1802, vol. x. p. 460. 



Corallum plate-like or vasiform, similar to M. conferta and M. hyacinthus in habit, 

 2'5 cm. thick. Under surface flattened, forming an open network, without projecting 

 branchlets; branches 6 to 12 mm. diameter; the stouter ones are usually compressed 

 laterally so as to be oval in section. Corallites on the under surface very short, open bursi- 

 f orm or immersed, thus differing entirely from either M. conferta or M. hyacinthus ; they are 

 nearly 2 mm. diameter; outer part of the wall rarely 1-5 mm. long, the inner part not 

 prominent ; aperture nearly 1 mm. ; star imperfectly developed. Branchlets on the upper 

 surface rather crowded, usually arranged in groups of 2 to 5 along the course of each 

 branch ; length 9 to 14 mm., diameter 4 mm., scarcely tapering ; apices about 6 mm. apart. 

 Axial corallites cylindrical. To mm. diameter or slightly over, rarely over 1 mm. exsert; 

 wall thin and aperture large, with a star of 12 septa, none of which are very prominent. 

 Radial corallites short, spreading, round-labellate, with curved margin to the lip ; diameter 1'2 

 to 1'5 mm., length 1 "5, rarely 2 mm.; wall fragile; directive septa scarcely recognizable. 

 The corallites are more spreading than in M. conferta, and the apertures are quite distinct 

 when seen from above. Corallum rather porous ; surface and wall striate and echinulate. 



o2 



