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Show 1882.] MR. S. O. RIDLEY ON THE CORALLIIDiE. 231 lateral small branches on the sides of the large ones, the anteroposterior flattening, the rigidly anterior position of the verruca? of the general surface, their abrupt projection and truncate extremity, separate it from all other species; while the minute characters, such as the double spicular complement, with its very remarkable form no. ii.-absent as it is from two of the recent Coralliida in which the spicules are known, and approximating the genus (as it appears to m e to do) to the Melithaida, from its resemblance to the "Blattkeule " so widely distributed in that family-unmistakably show its true position to be by the side of Pl. johnsoni. The chief differences between the species are the red colour of the greater part of the hard axis and of the cortex, the absence of the terminal tubercles to the cylindrical spicule no. i., and the smaller size of the verrucae, in the present form. Key to the Genera, Species, and Varieties. I have here endeavoured to present what appears to be the natural relations of the different forms, while giving characters which m ay readily distinguish them. I. Spicules of one kind, viz. octoradiate cylindrical. Verruca? distributed over whole surface of corallum, prominent, monticular CORALLIUM s. str. 1. Corallum branching in more than a single plane. i. Axis cylindrical; spicules about '09 m m . long. Known habitats. . . . , -, f C. nobile, } Mediterranean; a. Axis crimson, cortex red | typicalform. } Cape Verd Isl. 3. Axis and cortex yellowish- I C. nobile, j Mediterranean. white to white [ pale var. .. 0 . , „ . , f C. pallidum, u. Spicules ?; axis pale i ?_•* C .rubrum. f Fossil: Tertiaries of Italy and Scinde; not earlier than Miocene. 2. Corallum branching in but one plane, calicles sunk in pits in axis. Axis oval in transverse section, white; spicules about '06 m m . long; cortex very pale orange, very thin C. stylasteroides. Mauritius. II. Spicules of two kinds, radiate cylindrical and opera-glass-shaped ; calicles rising abruptly, truncate, those of stem and main branches confined to anterior surface. Corallum with lateral pinna? to main branches. Axis oval in transverse section PLEUROCORALLIUM, Gray, emend. 1. Axis partly red, partly white; cortex scarlet. i. Calicles chiefly on lateral pinna? ... Pl. secundum]..." Sandwich Is. ? " ii. Calicles chiefly on main branches ; cylindrical spicules normally 6- r pL secund -, radiate i „„„ ... ' ^Japan? var. elatior 2. Axis white, cortex cream-coloured; cylindrical spicules normally 8- radiate Pl. johnsoni Madeira. III. (incertcs sedis). Oorallmn with branches , CoralUum \ Fossil; White anastomosing-, apnoes nodose | ^ . . I ^ p |
