MADREPORA. 43 
of dimidiate corallites. Usually the two directive septa are recognizable, but the other 
primaries cannot be distinguished. Corallum very open and reticulate in section in the more 
slender parts, but very dense near the base; surface fenestrated and echinulate ; wall striate, 
scarcely echinulate unless near the base. 
Pacific Ocean: Great-Barrier Reef. 
a-c. Palm Island. Saville-Kent Coll. 92.6. 8. 60 to 62. (Types.) 
d. Herring Island, Bowen. Saville-Kent Coll. 92. 6. 8. 314. 
Variety : 
a. Rocky Island. Saville-Kent Coll. 92. 6. 8. 261. 
b. Branches usually under 1°5 cm. in thickness. 
21. Madrepora formosa. 
Madrepora formosa, Dana, Zoophytes, p. 473, pl. 38. fig. 4, pl. 31. fig. 2; M.-Edwards & Haime, 
Coralliaires, t. iii. p. 146; Verrill, Bull. Mus. Comp. Zool. 1864, vol. i. p. 41; Studer, MB. 
Akad. Wiss. Berlin, 1878, p. 533, pl. ii. figs. 7 & 8; Rathbun, Proc. U.S. Nat. Mus. 1887, 
vol. x. p. 15; ? Ortmann, Zool. JB. 1889, Bd. iv. p. 504. 
Madrepora brachiata, Dana, Zoophytes, p. 474, pl. 38. fig. 3; M.-Edwards & Haime, Coralliaires, 
t. iii. p. 147; Verrill, Bull. Mus. Comp. Zool. 1864, vol. i. p. 44; Studer, MB. Akad. Wiss. 
Berlin, 1878, p. 533; Rathbun, Proc. U.S. Nat. Mus. 1887, vol. x. p. 12; Ortmann, Zool. JB. 
1889, Bd. iv. p. 503. 
Corallum shrubby arborescent, slender and much divided. Branches 5 to 12 mm. thick ; 
branchlets often curved, subalternate, proliferous near the apex, 2°5 to 5 cm. long and 7 mm. 
thick, gradually tapering. Axial corallites cylindrical, 2 mm. diameter, 1 to 2 mm. exsert, 
aperture small. Radial corallites slender, tubular, all spreading, but the angle varies con- 
siderably, often at right angles; diameter 1 to 1:3 mm., length 15 to 3 mm., with an 
occasional elongate and thicker proliferous corallite. The corallites become shorter with a 
broader base in the older parts of the corallum. A few very short and small tubular corallites 
occur between the more prominent ones to near the tips of the branches, but none are truly 
immersed. The primary septa of the axial corallites are very well developed and subequal, 
second cycle absent or rudimentary ; the radial corallites have six moderately prominent 
septa, the directives being usually best developed. Corallum rather dense; surface dense and 
finely echinulate, subreticulate in parts ; wall substriate, echinulate. 
Var. brachiata. 
Corallum spreading arborescent.; branches elongate, straight, 1 to 2 cm. thick, the upper 
ones often 7 or 8 em. long. Axial corallites over 1 mm. exsert, short cyclindrical. Radial 
corallites subequal, short tubular, almost at right angles, becoming wart-like below. Aper- 
ture usually oblique but variable, 0°5 to 0°7 mm. diameter. Star distinct, the directive septa 
prominent. Corallum dense, surface finely granular, wall very minutely striate. (Dana.) 
