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Show 746 .' MR. 3. STANLEY GARDINER ON [June 6, Hydnophora exesa, H. demidoffi, and H. polygonata, Milne- Edwards & Haime, Cor. ii. pp. 420-422 (1857) (which see for other earlier references). Milne-Edwards and Haime stated their opinion that the three species above mentioned would be found to be different stages of growth of one species. M y specimen, on which I venture to propose the absorption of H. demidovii and H. polygonata, is a, colony 13 by 11 cm. across and 8 cm. high. The underpart is dead," but the upper parts have sent out over it a thin growing edge, free in places for 2-3 cm. The upper surface is a mass of low anastomosing branches and lobes, varying from 7 m m . to 2*5 cm. in diameter, of nearly all the same height, dead in three places, where they had apparently reached the surface and become exposed to the sun at low tide. The thin growing-edge is very fine, aud its monticules have the general character of those given by Milne-Edwards and Haime for H. exesa, save ouly that, owing to the irregular surface over which the edge is growing, the valleys are seldom more thau 4 m m. broad. The under surface is similar to that described for H. demi-clqffi, but the epitheca is in many places thick and well-marked. The length of the monticules on the lobes varies from 2 to 7 mm., being commonly greater on the larger and more central lobes. The monticules vary up to 6 m m . from one another, and up to 7 m m . in height. Large and small septa alternate one with another, the large alone fusing in the centre of the valleys. The septa are not so thick, and are nearer to one another than in H. lobata ; their edges, too, are rougher, and have no conspicuous teeth as in that species. The calicinal centres are not recognizable on the lobes, but on the thin growing-edge are fairly distinct. (Pl. XLVIII. fig. 3.) Funafuti ; outer reef. Quelch distinguished a species, H. tenella, in his ' Challenger' -Report, from H. exesa and H. demidoffi mainly by its mode of growth. I have already pointed out the great differences between the Wakayau reef-specimens of H. microcona and the Funafuti lagoon-specimens, and it seems to m e to be probable that this is a case of a new species having been described when simply different conditions prevailed, causiug different rates of growth. Whether the specimen above referred to //. exesa is really that species or H. polygonata, there seems to be no doubt but that H. tenella is only a synonym of H. exesa. Genus GONIASTRCEA. Goniastrcea, Milne-Edwards & Haime, Compt. rend, de l'Acad. des Sc. xxvii. p. 495 (1849), and Cor. ii. p. 444 (1857). This genus is easily distinguishable from Astrcea by the possession of distinct pali. These are joined at first to the septal edges by trabeculae, but later the connection becomes a distinct plate, so that they appear in section like thickenings of the septal edges. |