Madrepora in the Jh-itish Musemn. 459 



branclied specimens wliicli probably constitute a distinct 

 variety. Star well developed, primary septa broad and sub- 

 equal, the others not so prominent ; wall finely and closely 

 granular, echinulate, the echinulate plates often arranged in 

 rows at the base of the corallites. Immersed corallites are 

 not numerous, and occur only on the under surface of the 

 branches. 



Indo- Pacific Ocean; Singapore; N.E.Australia. 



Madrepora dathrata. 



Corallum fan-shaped, reticulate, 30 centlm. high, breadth 

 across the upj)er part 33 centim., but becoming rapidly nar- 

 rower below. A main stem is absent and the branches in the 

 lower part have a diameter of about 1 centim. ; their sub- 

 divisions are at iirst only slightly spreading, but become 

 more divaricate above. The branchlets are numerous, 2 to 4 

 centim. long and 5 millim. thick, frequently arched and laid 

 across one another at various angles, the whole fused together 

 into an irregular network, the n)eshes of which vary from 4 

 to 12 millim. across. Apical corallites 2 millim. diameter, 

 1 to 2 millim. exsert, wall rather thick and cylindrical, witii 

 a flat or slightly rounded apex ; the star consists of six sub- 

 equal septa of moderate development. Lateral corallites on 

 the anterior (superior?) surface very unequal, not very 

 crowded; the larger ones tubular, at right angles, with an 

 oblique aperture, from 3 to 4 millim. long and about 2 millim. 

 diameter, but frequently a little compressed; a few are longer 

 and proliferous, the remainder are less spreading, shorter, 

 tubular, tubo-nariform, and nariform to subimmersed ; the 

 only truly immersed corallites on the upper surface occur in 

 the lines ot fusion. Star imperfect, the directive septa mode- 

 rately developed, but the others are rudimentary or wanting. 

 The lateral corallites on the posterior (inferior?) surface are 

 distant, very short, chiefly subimmersed or cochlear! form. 

 Corallum very porous, surface closely reticulate and echinu- 

 late, the echinulations often plate-like. Wall of the apical 

 corallites and of the elono-ate lateral ones costate above, the 

 ccstaj being echinulate below ; wall of the remaining lateral 

 corallites echinulate in rows. 



Indian Ocean ; Mauritius. 



Madrepora compJanata. 



Corallum flabellate, probably about 23 centim. high and 40 

 centim. broad. The main stem gives off alternate branches 



