224 MR. S. 0. RIDLEY ON THE CORALLIID, [Feb. 7, 
opera-glasses, or of two short globose bottles united by their sides ; 
consists of two globose masses, often somewhat flattened at distal 
end, separated by a more or less deep constriction, their surface 
microtuberculate ; to the proximal extremity of each is attached a 
short handle-like process, of variable shape, bearing several long 
tubercles, and About one third the length of the larger lobes; average 
maximum size °053 mm. long by ‘053 mm. across the two lobes; 
thickness of lobes, antero-posteriorly, about -044 mm. 
The thickness of the cortex appears to be correlated with the 
smoothness of the hard axis in the stem (higher up this is distinctly 
striated) ; for in the other species of Hemicorallium, H. secundum, the 
thinner cortex appears to be associated with a striated stem. The 
explanation (physiological) appears to be that the ccenosarcal canals, 
which would have grooved the surface of the axis, find sufficient 
protection in the cortex when this is thick. 
Turning to O. (Pleurocoralliwm, Gray) secundum, Dana (U.S. 
Expl. Exp., Zoophytes, vol. vii. p. 641, Atlas, Zooph. pl. lx. fig. 1), 
we find again the mode of branching to be substantially that in one 
plane; here too the polypes are said to be confined to the front or 
sides of the branches, but to be borne mostly on small branchlets or 
pinne scattered over the edges and front of the main branches—an 
arrangement differing from that of both the preceding forms, but 
agreeing with that to be described below in the new species C. stylas- 
teroides, with which this species further agrees in the growth in one 
plane. Unfortunately the spicular characters are unknown ; but, 
from resemblances which have been found to exist between this and 
a form described below as a variety of it and agreeing in all generi- 
cally important characters with Hemicorallium johnsoni, I have little 
doubt of its similar generic identity with that species: therefore one 
of the genera Pleurocorallium and Hemicorallium must give way, 
and the former must stand, having precedence in description. 
Hemicorallium therefore = Pleurocorallium; and Hemicorallium 
johnsoni= Pleurocorallium johnsoni. 
Looking at the relations of C. nodile to the species described 
below as new under the name of C. stylasteroides, we find a thin 
cortex in both, a low polype-verruca, and a spicule differing only in 
size; and it is only in those characters which, as I have stated, I 
believe to be less essential in the classification of this Order, viz. 
mode of branching, colour, and form of axis (?.¢. cylindrical or 
oblong in section), that we find great differences ; and the first two 
of these have been already seen to vary widely in C. rubrum, and in 
their variation to approximate that species to C. stylasteroides. 
No other recent species has been described. 
The only other species with which I am acquainted are the fossil 
forms C. pallidum, Michelin (Iconogr. Zoophytol. p. 16, pl. xv. fig. 9), 
from the Miocene of Italy and Tertiaries of Scinde, and C. bechii, 
M.-Edw. and Haime (Distr. méth. polyp. paleeoz. p. 188), from 
the White Chalk of Faxde. The former is distinguished from our 
species by having the method of branching of C.. nobile, viz. cylin- 
drical branches given off at considerable intervals ; and it appears to 
