466 Mr. G. Brook on new Species of 



diameter, slightly prominent, wall thick and porous. Lateral 

 corallites tubular and appressed above, shorter and more 

 spreading near the base. Length 1 to 4 millira.^ diameter 

 1 to 1'5 millim. Aperture large ; wall thin compared with 

 other species of the subgenus. Surface finely clothed with 

 longitudinal series of dentate plates. 



The species differs from all others of the subgenus in the 

 possession of thin-walled lateral corallites. 



Tongatabu («/. J. Lister , Esq.). 



Madrepora polymorpha. 

 Madrepora ahrotanoides, Dana (non Lamarck), Zoophytes, p. 477, 

 pi. xli. fig. 1 ; Verrill, Bull. Mus. Comp. Zool. vol. i. 1864, p. 41 ; 

 Rathbun, Proe. U.S. Nat. Mus. vol. x. 1887, p. 12. 



Corallum fruticose, spreading, ramose ; branches 8 to 20 

 centim. long, usually about 1*5 to 2 centim. thick, gradually 

 tapering ; the branches bear numerous branchlets, spreading 

 usually at an angle of 80° to 90°, and varying in importance 

 from thickened and elongate proliferous corallites to subterete 

 and tapering twigs 4 centim. long and 1 centim. thick. 

 Apical corallites 1'5 to 2 millim. diameter arid 0*5 to 2 millim. 

 exsert ; wall thick or comparatively thin. Lateral corallites 

 compressed, nariform, or tubo-nariform, unequal, the longer 

 ones becoming tubular and proliferous ; some distance below 

 the apex all become verruciform, with a dilated wall, which 

 gradually becomes reduced to a ring-shaped fold. Immersed 

 corallites are usually wanting, even in the older parts of a 

 colony ; but in one or two s|)ecimens which agree closely in 

 other respects immersed corallites may take tiie place of those 

 ■with a ring-shaped lip. Lateral corallites 1'5 millim. dia- 

 meter or under and 1'5 to 3 millim. or more in length ; aper- 

 ture oval, wall varying in thickness in different specimens ; 

 always thickened some distance below the apex of a branch, 

 and ill some cases quite to the apex ; in the latter case the 

 wall of the apical corallite is also thickened. The apical 

 corallites are provided with twelve septa, none of which are 

 very prominent ; those of the lateral corallites are also usually 

 narrow, including the directives ; in the corallites situated 

 some distance from the apex the second cycle is almost as 

 well developed as the first. Corallum dense, even near the 

 apex of a branch in most specimens ; surface and wall finely 

 and closely echinulate. 



Indo-Pacific Ocean ; Malacca ; Fiji ? 



Madrepora polystoma. 



Corallum corymbose and complanate below, 35 centim. 

 wide and 12 centim. high, closely resembling that of M. con- 



