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Show 1882.] MR. S. O. RIDLEY ON THE CORALLIID^?. 223 cation, recourse has to be had mainly to the characters of the spicula and of the verruca?. The want of good series of individuals of any known species of Coralliida except C. nobile is an obstacle to the full discussion of the natural relations of the different forms; a few facts only can be noted at present as bearing on the subject. Beginning with the comparatively common Corallium nobile, Pallas (rubrum, Costa) we find a cylindrical axis, usually branching seldom, but dicho-tomously and most commonly in an arborescent manner, which, though tending towards growth in one plane, yet almost invariably is actually in various planes ; the cortex quite conceals any inequalities of the surface; and the verruca?1 (orcalicles) project dome-like from all sides of the branches. Variations are frequent, especially in mode of growth; but these are by far the commonest characters of the species. The colour of the axis varies not uncommonly from crimson to pale red, rarely to yellow, and more rarely to white; the spicules are of one type, viz. a hexahedral oblong form, the angles being formed by broad truncate but microtuberculate tubercles, which preserve the chief features of their characteristic form throughout all varieties of the external form of the coral. (Cf. Lacaze-Duthiers, Hist. Nat. Corail, p. 7 0 - " toutefois en recherchant bien, on finit par decouvrir une forme qui, resumant toutes les autres, peut etre regardee comme la type.") Corallium (Hemicorallium, Gray) johnsoni, P. Z.S. 1860, p. 393, Radiata, pl. xviii., differs in several particulars from the former species, besides the branching essentially in one plane, the strictly anterior position of the verrucae, and their considerable protrusion from the surface, which are the chief points insisted on by Dr. Gray. Thus the cream-coloured cortex is about *5 m m . thick, about twice the thickness which it has in C. nobile; on the terminal branches the calicles rise abruptly from the surface, are truncate above, and measure 1*5 to 2 m m . in average diameter. The spicules have not hitherto been described; and their characters, in the one case, are so remarkable, and have such an important bearing on the affinities of both the genus and family to which the species belongs, that I now proceed to describe them. Spicules of two kinds:-(i.) cylindrical, octoradiate, having a short stout shaft terminated at each end by a tubercle; two pairs of tubercles also project from each end of the shaft, in the same plane as the terminal ones, but at right angles to its long axis ; on the anterior side (reckoning the two pairs of tubercles just mentioned as lateral) a tubercle projects at right angles to the long axis of the shaft, and also to the plane in which the lateral tubercles lie ; on the posterior side a similar tubercle is similarly placed, but at the opposite end of the spicule ; the ends of the short, broad, truncate tubercle are microtuberculate with few, sharp, smaller tubercles; size -08 by *053 m m . : this form is exactly similar to that of C. nobile, but is slightly smaller. Spicule no. ii. bilobate, having the form of a pair of 1 I think it best to adopt Verrill's term for those parts of the cortex which are specialized for the reception of the polypes. |