79 MADEEPOEARIA. 



branchlets from a common base. Branchlets 6-7 cm. long and 1-2 cm. thick, truncate at the 

 summit. Radial corallites crowded and acervate at the summit of the branchlets, very un- 

 equal, some 6 mm. long and others obsolete ; majority appressed, tubiform, and slender ; 

 lip elongate ; exterior smooth ; aperture often oblong j star scarcely distinct. Axial coral- 

 lites difficult to distinguish. {Dana.) 



The ' Challenger ' specimen referred by Quelch to this species agrees with Dana's 

 diagnosis in most respects. The branches are 5 to 6-7 cm. long, 1*5 cm. thick, and quite 

 blunt at the apex. Axial corallites 25 mm. thick, 1 to 2*5 mm. exsert ; wall rather thick, 

 but tapering ; septa in two cycles, the primaries well developed. Radial corallites tubular, 

 spreading irregularly and quite unequal in length and diameter. Prominent corallites 4 

 to 7 mm. long and I'o to 2"3 mm. diameter; aperture usually oblique; wall scarcely 

 thickened ; septa not well developed, the outer directive stouter and broader than the others ; 

 sometimes a second cycle may be distinguished ; the larger corallites frequently bear a 

 single nariform bud; a few very small immersed or subimmersed corallites are scattered 

 between the others ; surface strongly echinulate ; on the walls of the coraUites the echinula- 

 tions are arranged in close longitudinal rows. 



Another specimen from the same locality, referred to M. plantaginea by Quelch, may be 

 a variety to this species. The apices of the branches are proliferous and less obtuse than in 

 typical specimens, and the axial corallites, though readily recognizable, are scarcely stouter 

 than some of the radial ones ; the more prominent radial corallites have a relatively thick 

 wall with rounded margin. 



Pacific Ocean : Fiji, Tahiti. 



a. Tahiti. H.M.S. 'Challenger.' 86.12.9.238. 



i. Tahiti. H.M.S. 'Challenger.' 86.12.9.25.0. {= M. plantaginea, Q,ndch.) 



b. Branchlets rarely over 6 mm. thick. Corallites tubular to tubo-labellate ; 

 wall usually thin and fragile. 



65. Madrepora decurrens. 



Heteropora decurrens, Ehrenberg, Corallenth. d. roth. Meeres, p. 111. 

 Madrepora decurrens, Dana, Zoophytes, p. 488. 



The type specimen, which is preserved in the Berlin Museum, consists only of fragments ; 

 the habit of the species is probably corymbose. One fragment, 8 cm. high and 10 cm. wide, 

 consists of a cluster of branchlets 5 cm. long and 1 cm. thick at the base (including coral- 

 lites), most of which are proliferous. Axial corallites 2 to 2-2 mm. diameter and 2 to 3 mm. 

 exsert, wall very porous and fragile ; the star consists of six well-developed primary septa, 

 which often meet in the middle line, and of a narrower second cycle. Radial corallites large, 

 thin-walled, elongate tubular, rather distant, at an angle which does not usually exceed 30° ; 

 length 4 to 6 mm., diameter 2 mm. ; aperture oblique or, in some cases where the inner part 

 of thewall is scarcely developed, the form is tubo-labellate. A few very short and sub- 

 immersed corallites are scattered between the others. On the under surface of the branches 



