46 MADEEPOEAEIA. 



E. Prominent corallites of different sizes and shapes intermixed. 

 a. Corallum bushy arborescent. 



24. Madrepora valenciennesi. 



Madrepora valenciennesii, M.-Edwards & Haime, Coralliaires, t. iii. p. 137 ; (? non Ortmann, Zool. JB. 

 1889, Bd. iv. p. 503). 



Corallum arborescent, about 18 cm. high ; branches cylindrical and subulate, several 

 rising to a similar height from a common base, diverging in all directions, subdivided some- 

 what as in M. nobilis. Main branches 1*8 cm. diameter, gradually tapering to a large axial 

 corallite. Subdivisions spreading and simple up to 8 cm. in length. Axial corallites 4 to 

 4'5 mm. diameter and 2'5 mm. exsert, with a very thick porous wall ; septa in two cycles, 

 both moderately developed. Radial corallites tubular or half-tubular, spreading nearly 

 at right angles ; very variable in size, 1 to 2 mm. diameter, the larger ones with a thicker 

 wall. Corallites of various lengths intermixed, those up to 4 mm. in length remain simple, 

 the longer ones bear a few bud-coralliteSj and the axial corallite is then thickened ; there are 

 no truly immersed corallites. There is only one cycle of septa in those corallites not destined 

 to become proliferous ; the directive septa are very broad and nearly meet in the middle line, 

 the others are narrow. Corallum very fragile and spongy-reticulate throughout; wall fragile 

 or very porous, striato-reticulate. 



The above description is based on the type in the Paris Museum. 



Indo-Pacific Ocean : Ceylon, Torres Straits. 



a-c. Thursday Island. Saville-Kent Coll. 92. 6. 8. 63 to 65. 



25. Madrepora laxa. 



Madrepora laxa, Lamarck (non Ehrenberg, non Briiggemann, &c.). Hist. Nat. Anim. sans Vert. t. ii. 



p. 280, ed. 2, p. 448 ; Blainville, Man. d'Actin. p. 390 ; Deslongchamps, Encyclop. p. 504 ; 



Dana, Zoophytes, p. 487; M.-Edwards & Haime, Coralliaires, t. iii. p. 146; (non Quelch, 



' Challenger ' lleef Corals, p. 156). 

 ? Madrepora pharaonis, Briiggemann (non M.-Edw. & H.), Phil. Trans. 1879, vol. clxviii. p. 574. 



Corallum arborescent, laxly branched; branches spreading, terete, slowly tapering. 

 Axial corallites 2 mm. diameter, a little prominent, wall not specially thickened. Radial 

 corallites small, tubular, mostly at right angles or nearly so ; crowded and unequal in length 

 in front, becoming short and immersed on the reverse aspect of a branch ; diameter 1 to 

 1*5 mm., length to 2*5 mm. Scattered at rather considerable intervals are a few proliferous 

 corallites of 6 mm. in length and 2 mm. diameter at the apex, spreading at right angles ; 

 they form short branchlets at a later stage. Septa variable, usually the directives are of 

 considerable breadth ; the outer primaries narrow, and the second cycle still narrower. 

 Corallum moderately porous in section ; surface dense, finely tabulato-echinulate throughout ; 

 wall not costulate. 



