MADEEPOEA. 



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 ecliinulate j wall striate, 

 scarcely echinulate unless near the base. 



Pacific Ocean : Great-Barrier Reef, 



a-c. Palm Island. 

 d. Herring Island, Bo wen. 



Variety : 



a. Rocky Island. 



Saville-Kent Coll. 92. G. 8. 60 to 62. (Types.) 

 Saville-Kent Coll. 92. 6. 8. 314. 



Saville-Kent Coll. 92. 6. 8. 201. 



b. Branches usually under 1*5 cm. in thickness. 



21. Madrepora formosa. 



Madrepora formosa, Dana, Zoophytes, p. 473, pi. 38. fig. 4, pi. 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, pi. ii. figs. 7 & 8 ; Eathbun, Proo. U.S. Nat. Mua. 1887, 



vol. X. p. 15 ; ? Ortmann, Zool. JB. 1889, Bd. iv. p. 504. 

 Madrepora hrachiata, Dana, Zoophytes, p. 474, pi. 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 ; Eathbun, 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 1*5 to 3 mm., with an 

 occasional elongate and thicker proliferous corallite. The corallites become sliorter 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. hrachiata. 

 Corallum spreading arborescent ; branches elongate, straight, 1 to 2 cm. thick, the upper 

 ones often 7 or 8 cm. 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, 05 to 07 mm. diameter. Star distinct, the directive septa 

 prominent. Corallum dense, surface finely granular, wall very minutely striate. {Dana.) 



