1882.] MR. S. O. RIDLEY ON THE CORALLTID^. 223 



cation, recourse has to be had mainly to the characters of the spicula 

 and of the verrucae. 



The want of good series of individuals of any known species of 

 CoralliidcB 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 verrucae^ (or calicles) 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. 70 — " toutefois en recherchant bien, on finit par 

 decouvrir uue forme qui, resumant toutes les autres, pent etre regardee 

 comme la type.") 



Corallium {Hemicorallium, Gr &j) joAnsoni, P. Z. S. 1860, p. 393, 

 Radiata, pi. 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 mm. 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 mm. 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 afl&nities 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 micro- 

 tuberculate with few, sharp, smaller tubercles ; size '08 by '053 mm.: 

 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 



^ I thiuk it best to adopt Verrill's term for those parts of the cortex which 

 are specialized for the reception of the polypes. 



