OCR Text |
Show 1899.] ASTRcEID CORALS FROM THE SOUTH 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, and in the older calicular centres is often 4-5 m m . across and covered on the surface with fine, small spines. Rotuma; 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, aud are very common in the outer half of the boat-channel. The species is noticeably resistant to the action of the sun, parts of tbe 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 XLVIII. fig. 1), as the differences 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 LEPTORIA. Leptoria, Milne-Edwards & Haime, Compt. rend, de l'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. LEPTORIA GRACILIS Dana. Mceandrina gracilis, Dana, Zooph. p. 261, pl. xiv. fig. 6 (1848). Leptoria gracilis, Milne-Edwards & Haime, Cor. ii. p. 407 (1857). Leptoria gracilis, Klunzinger, Die Korall. des R. Meeres, iii. p. 13, pl. 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 m m . 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 m m . in depth, and are closed in below by horizontal endothecal dissepiments. Rotuma; outer reef. 2. LEPTORIA TENUIS Dana. Mceandrina tenuis, Dana, Zooph. p. 262, pl. xiv. fig. 7 (1848). Leptoria tenuis, Milne-Edwards & Haime, Cor. ii. p. 407 (1857). A single specimen, which corresponds very closely to Dana's |