189'J.] ASTR^ID COKAES FROM THE SOTTTH PACIFIC. 739 



are joined by 3-5 septa, the inner ends of the original septa, and 

 the septa on the walls of the valleys bend round towards them. 

 The columella is formed of the twisted septal ends, aud in the 

 older calicular centres is often 4-5 mm. across and covered on the 

 surface with fine, small spines. 



Eotuma ; boat-channel. 



The species in the living condition is of a green colour, brown 

 round the peristome. The colonies form great hemispherical 

 masses, 2-3 feet across, and are very common in the outer half of 

 the boat-channel. The species is noticeably resistant to the action 

 of the sun, parts of the colonies at spring tides being uncovered 

 for 2-3 hours. Massive colonies, too, which have died in the centre 

 and been hollowed out are rare. 



I have added a photo-figure (Plate XLYIII. fig. 1), as the 

 difEerences in the septal orders, &c. are not clearly and accurately 

 shown in the previous figures, nor do these figures correspond to 

 the descriptions of their authors. 



Genus Leptobia. 



Leptoria, Milne-Edwards & Haime, Compt. rend, de I'Acad. des 

 Sc. xxvii. p. 493 (1848), and Cor. ii. p. 405 (1857). 



Two dried specimens, which appear to belong to the same two 

 species as Dana found in Fiji. The genus is nowhere common, 

 and indeed I found only one patch of each species. 



1. Leptobia gbacilis Dana. 



Mceandrina gracilis, Dana, Zooph. p. 261, pi. xiv. fig. 6 (1848). 



LeiJtoria gracilis, Milne-Edwards & Haime, Cor. ii. p. 407 (1857). 



Leptoria gracilis, Klunzinger, Die Korall. des E. Meeres, iii. 

 p. 13, pi. ii. fig. 5 (1879). 



A single reef -specimen, having the general facies given by Dana. 

 The septa are continuous over the winding thecal walls, in some 

 places being about -7 mm. exsert. The theca is apparently a 

 pseudo-theca, formed by thickenings on the sides of the septa. The 

 upper edges of the fused septa are almost horizontal over the theca, 

 the edges towards the valleys being almost perpendicular. The 

 edges of the septa are finely denticulate, and there are 14-16 septa 

 in 1 cm. The columella is a thin imperforate plate in the valleys, 

 and to it all the septa are fused. Its upper edge is covered with 

 blunt, almost square lobes, about 7 in 1 cm. The interseptal loculi 

 vary from 5-8 mm. in depth, and are closed in below by horizontal 

 endothecal dissepiments. 



Eotuma ; outer reef. 



2. Leptoria tets'uis Dana. 



Mceandrina tenuis, Dana, Zooph. p. 262, pi. xiv. fig. 7 (1848). 

 Leptoria tenuis, Milne-Edwards & Haime, Cor. ii. p. 407 (1857). 

 A single specimen, which corresponds very closely to Dana's 



