42 MADREPOEAEIA. 



19. Madrepora roT)Usta. 



Madrepora robusta, Dana, Zoophytes, p. 475, pi. xxxix. fig. 3 ; M.-Edwards & Haimo, Coralliaires, t. iii. 



p. 137 ; Verrill, Bull. Mus. Comp. Zool. 1864, vol. i. p. 40 ; Quelch, ' Challenger ' Eeef Corals, 



p. 151 ; Eathbun, Proc. U.S. Nat. Mus. 1887, vol. x. p. 18. 

 tHeteropwa eervicomu, Ehrenberg (non Lamarck), Corallenth. d. roth. Meeres, p. 110. 



Corallum very stout and laxly branched ; branches up to 4 cm. thick and 30 cm. long, 

 terete, only slightly tapering, excepting in some of the terminal divisions, apices blunt. 

 Ultimate branches 5 to 10 cm. long, and simple or occasionally bearing a cluster of smaller 

 branchlets near the apex; diameter 3 to 3 cm. near the base and 1 to 1-5 cm. close to the 

 apex. Axial corallites scarcely distinguishable from the radial tubular ones, rarely 3 mm. 

 diameter (usually 2 to 2'5 mm.), and about 2 mm. exsert. Radial corallites spreading at 

 right angles or nearly so, rather crowded, but of unequal length; about one third are tubular 

 with circular or slightly oval aperture, a little over 2 mm. diameter and 1 to 2 mm. in length; 

 wall rather thick and porous. Those between are dimidiate, nariform, or subimmersed. 

 Directive septa sometimes well developed, the other primaries narrow; a second cycle is 

 usually represented in rudiment. Corallum dense, surface spongy, wall strongly and evenly 

 costate. 



Pacific Ocean : Fiji. 



a, J. Fiji. H.M.S. 'Challenger.' 86. 12. 9. 226 & 414. 



c', d. ? Sir E. Home, Bart. [P.] . 47. 1 . 1. 2 & 3. 



e-g. ? ? 58. 2. 10. 3,4 & 6. 



20. Madrepora grandis. (Plate I. figs. A, B.) 



Madrepora gravdis. Brook, Ann. Mag. N. H. 1892, vol. x. p. 457. 



Corallum stout, arborescent, laxly divided. One specimen, which consists of the distal 

 part of a colony, is 36 cm. long, and the main branch is 3 cm. in diameter. Branches simple 

 or forked, some which are 17 cm. long and 2 cm. thick are simple, slowly tapering, attenuate. 

 Near the apex of a colony tlie divisions are, however, sometimes much shorter and more 

 numerous. Axial corallites 3 mm. diameter, cylindrical, considerably exsert (2 to 3 mm.) ; 

 •wall very porous; star moderate or well-developed. On the distal 5 cm. of a branch 

 the radial corallites are ascending tubular, with thin wall and deep large cup, practically 

 without septa; length 4 to 5"5 mm., usually cylindrical, but sometimes a little compressed, 

 2 mm. diameter, inner part of the wall as prominent as the outer. Such prominent corallites 

 are about 5 mm. apart, with smaller tubular, nariform, or subimmersed between, diameter 

 about 2 mm. ; wall usually thin, but a little thicker in the more elongate corallites. Below 

 the distal 5 cm. (approximately) of a branch, all the radial corallites extend at right angles 

 to the axis and none are over 2 mm. long ; they are tubular in form and become gradually 

 shorter towards the base. The condition differs from that of M. robusta in similar situations 

 in the thinner wall, in the absence of a recognizable star of septa, and also in the absence 



