OCR Text |
Show 1899.] ASTRc-EID CORALS FROM THE SOUTH PACIFIC. 737 of the endotheca in all is very similar, forming thin plates across the interseptal loculi, which may be arranged, according to the form of growth, in almost any position from horizontal to vertical. 1. MUSSA CACTUS Dana. Mussa cactus, Dana, Zooph. p. 178, pl. vii. fig. 1 (1848). I have referred seven specimens to this species, with which two or three of those described by Milne-Edwards and Haime would also seem to be identical. All the specimens were obtained from the same locality, and in the colour of the living polyps conformed perfectly to Dana's fig tire and description :-" Disk green ; inner tentacles bursiform, pearl-white, and brown at tip, outer a little elongate and brown." The broad pad of tissue in the contracted polyps round their edges is very well-marked in m y spirit specimens as in Dana's figure. The corallites, however, tend to be more irregular iu outline, and form in the centres of the colonies longer series than are represented b} Dana. The polyp extends for 1-1*5 cm. down the outside of the corallum, and below this there is a thin, incrusting epitheca. The costae are marked solely by a few, upwardly directed, pointed spines about 1 m m . high and 3-4 m m . distant one from another. The columella is well marked, and formed of twisted lamella? from the septal edges, without any distinct surface spinulation. Rotuma; found only in certain reef-pools off Solkopi. 2. MUSSA CRISTATA Esper. Madrepora cristata, Esper, Pflanz. i. p. 150, Madr. pl. xxvi. (1791). Mussa cristata, Milne-Edwards & Haime, Cor. ii. p. 335 (1857). I have referred four specimens to this species, which agree fairly well with tbe above descriptions. They do not bear, however, much resemblance to Esper's figure, the spinulation of the septa not being different from that of other members of the genus, and the costae not being so marked, although without spines as in the figure. The polvps extend for 1*5-2 cm. down the outside of the corallum, and the ribbed appearance below their edges is in one specimen nearly as distinct as in Esper's figure. These ribs appear fo> be due to the retreating polyp laying down a thin epitheca behind it, which in places forms arches over the costae, which themselves broaden out. The columella is well developed and of a spongy structure, with no spinulation on its surface. Rotuma; boat-channel. The livino* polyps are of a light olive-green colour. 3. MUSSA MULTILOBATA Dana. Mussa multilobata, Dana, Zooph. p. 181, pl. viii. fig. 2 (1848). Mussa multilobata, Milne-Edwards & Haime, Cor. ii. p. 336 (1857). This identification is, like that of Mussa cactus, largely based on |