40 MADREPORARIA, 
16. Madrepora arbuscula. 
Madrepora arbuscula, Dana, Zoophytes, p. 474, pl. xl. fig. 2; M.-Edwards & Haime, Coralliaires, t. iii. 
p- 188; Verrill, Proc. Essex Inst. 1866, vol. v. p. 21; ? ibid. 1869, vol. vi. p. 69; Verrill, Bull. 
Mus. Comp. Zool. 1864, vol. i. p. 41; Studer, Mitth. naturf. Ges. Bern, 1880, p. 19; Rathbun, 
Proe. U.S. Nat. Mus. 1887, vol. x. p. 12; Ortmann, Zool. JB. 1888, Bd. iii. p. 149. 
? Madrepora scabrosa, ? B.-Smith (non Quelch), Ann. Mag. N. H. 1890, vol. vi. p- 452. 
Corallum arborescent, much branched, forming bushy clumps 30 em. high and 40 em. in 
diameter from a stem 2 cm. thick. Branches spreading, terete, 8 to 18 mm. diameter, only 
slightly tapering. Upper branches often 8 to 11 cm. long, simple and very gradually 
attenuate. Axial corallites 2°5 to 3 mm. diameter and 2-5 mm. exsert, wall thick and porous. 
Radial corallites 1:5 mm. diameter and 3 to 4 mm. long, tubular, more or less ascending, and 
with a moderately thick wall; crowded on the superior surface, but more distant on the 
underside, becoming short and thick tubercles on the under surface of the stouter branches. 
Corallum porous and fenestrated in section, surface finely reticulate and echinulate; wall 
striato-reticulate when thin, becoming evenly echinulate with increase in thickness. All the 
primary septa are broad, the directives nearly meet in the middle line; second cycle 
inconspicuous. 
Indo-Pacific Ocean: Singapore, Sulu Sea, ? Japan, Great-Barrier Reef. 
a, ——? Mr. Sowerby [P.]. 45. 5. 21. 185. 
b. ——? Purchased. 59. 12. 12. 1. 
c. ——? ? 938.4. 7. 86. 
d,e. Palm Island. Saville-Kent Coll. 92.6.8.73 & 74. 
jf. Channel Rock Reef. Saville-Kent Coll. 92. 6. 8. 79. 
?g. Tizard Bank. H.M.S. ‘ Rambler.’ 89. 9. 24. 110. (=WM. scabrosa?, B.-Sm.) 
17. Madrepora virgata. 
Madrepora virgata, Dana, Zoophytes, p. 471, pl. xxxix. fig. 1; M.-Edwards & Haime, Coralliaires, t. iii. 
p- 145; Verrill, Bull. Mus. Comp. Zool. 1864, vol. i. p- 41; Studer, MB. Akad. Wiss. Berlin, 
1878, p. 533; Quelch, ‘Challenger’ Reef Corals, p. 158; Rathbun, Proc. U.S. Nat. Mus. 1887, 
Vol ex-ip.) LO! 
Madrepora gracilis, Quelch, ‘ Challenger’ Reef Corals, p. 158 (part.). 
Corallum slender, arborescent, spreading and remotely ramose; branches under 1 em. 
in diameter, very long, terete, subarcuate, not proliferous. Ccenenchyma scarcely porous, 
minutely granulous ; radial corallites small, rather crowded, very short and thin tubular ; 
margin acute, cell circular, star of six narrow rays. Terminal branches often 15 em. long, 
very gradually tapering. 
The above is a summary of Dana’s description: the ‘Challenger’ specimens referred 
by Quelch to this species differ in several important points. The ccenenchyma is very 
porous and reticulate in section, the surface is covered with closely-placed rows of dentate 
