MADEEPOEA. 131 



specimen from Rodriguez in which the cones are not present ; but as in consequence the 

 specific characters are not yet developedj the identity is uncertain. 



Indian Ocean : Rodriguez ; ? Great-Barrier Reef. 



a, b. Rodriguez. Royal Society [P.]. 76. 5. 5. 93 & 119. (Types.) 



c. Capricorn Islands. Saville-Kent Coll. 92. 6. 8. 49. 



Division II. 



5. Subgenus ISOPOEA. 

 Asi,r<m (part.), Lamarck. 

 Isadora, Studer, MB. Akad. Wiss. Berlin, 1878, p. 535. 



Corallum cormiform, consisting of several thick, blunt, plate-like branches from a 

 common base. The axial corallites are differently arranged to those in all other divisions of 

 the genus Madrepora. Usually each axial (parent) corallite forms the axis of a branch or 

 branchlet, and they therefore occur singly. In this subgenus they do not occur singly in 

 typical cases, but a considerable number of closely-arranged parent corallites occupy the 

 centre of each plate, and may be recognized at the margin by their circular wall and central 

 aperture. They are quite normal in form j it is only the fact that they are collected into 

 groups corresponding with the thickness and breadth of the plates that has led to their being 

 overlooked. Radial corallites usually thick-walled, tubular, or cochleariform. 



This subgenus correspouds with Dana's Section G of the genus Madrepora. 



A. Corallites cochleariform, with thick outer and thin^ more or less incomplete, inner wall. 



131. Madrepora palifera. 



Astrcea palifera, Lamarck, Hist. Anim. sans Vert. t. ii. p. 262 ; ed. 2, p. 409 ; Lamouroux, Encyol. 



p. 180. 

 ? Qemraipora palifera, BlainviUe {non Dana &c.), Manuel d'Actin. p. 387. 

 Madrepora labrosa, Dana, Zoophytes, p. 486, pi. xliii. fig. 3, pi. xxxi. fig. 10 ; M.-Edwards & Haime, 



Coralliaires, t. iii. p. 161 ; Eathbun, Proc. U.S. Nat. Mus. 1887, vol. x. p. 16 ; B.-Smith, Ann. 



Mag. N. H. 1890, vol. vi. p. 455. 

 Isopora labrosa, Studer, MB. Akad. Wiss. Berlin, 1878, p. 535. 



Corallum laminate, plates erect or spreading, obtuse, 2 to 8 cm. broad and 1*5 to 4 cm. 

 thick, margin rounded, apex blunt and usually flattened. Corallites at the apex tubular, but 

 usually not prominent, 3 mm. diameter. Walls very porous, 1 mm. thick or more, and 

 frequently confluent. There are two cycles of septa present, both rather narrow, but the direc- 

 tives are thicker than the others. Radial corallites cochleariform or tubular, with incomplete 



