1882.] MR. S. O. RIDLEY ON THE CORALLIID^. 231 



lateral small branches on the sides of the large ones, the antero- 

 posterior flattening, the rigidly anterior position of the verruciE 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 Coralliidce'vci which the 

 spicules are known, and approximating the genus (as it appears to me 

 to do) to the Melithaidce, from its resemblance to the "Blattkeule " 

 so widely distributed in that family — unmistakably show its true 

 position to be by the side of PI. johnsoni. The chief diiferences 

 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 verrucse, 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 may 

 readily distinguish them. 



I. Spicules of one kind, viz. octoradiate cylindrical. Ver- 

 rucffi distributed over whole surface of corallum, promi- 

 nent, monticular Corallium s. str. 



1 . Corallum branching in more than a single plane, 

 i. Axis cylindrical ; spicules about '09 mm. long. Known habitats. 



... i J [ C. nobile, \ Mediterranean ; 



Axia cnmson. cortex red \ ^^j^ '^^^^ | ^^^^ ^^^^ j;^^ 



Mediterranean. 



''Fossil: Tertiaries 

 of Italy and 

 Scinde ; not 

 earlier than 

 Miocene. 



/3. Axis and cortex yellowish- J C. nobile, | 

 white to white \ pale var. J 



.. ci • ^ n ■ 1 { C. pallidum 



n. Spicides?; axis pale [-iJcrubmn 



2. Oorallvun branching in but one plane, calicles sunk in 

 pits in axis. 



ks.s oval in transverse section, white ; 

 spicules about '06 mm. 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 pinnse to main branches. Axis oval in 

 transverse section Pleurocorallium, Graj*, emend. 



1. Axis partly red, partly white ; cortex scarlet. 



i. Calicles chiefly on lateral pinnae ... PI. secundum]..." Sandwich Is. ? " 



ii. Calicles chieflv on main branches : 



cylindrical spicules normaUy &- . pj secunchm, 1 . o 

 '^^'^t* t var.e/a^iar.r*P""^ 



2. Axis white, cortex cream-coloured ; 

 cylindrical spicules normally 8- 



radiate PI. johnsoni Madeira. 



III. (i,icerf<B scdi^). Oorallmn with branches , Corallinm 1 Fossil ; White 

 anastomosing. npicPs nodose | ^^^.^.. I Chalk of Faxoe. 



