228 MR. S. O. RIDLEY ON THE CORALLIID. [Feb. 7, 
considerable depth at which this specimen was obtained, not being 
greater than that from which Coralliwm is brought to the surface 
in the Mediterranean, need not of itself prevent such an undertaking. 
PLEUROCORALLIUM SECUNDUM, Dana, var. ELATIOR. (Plate IX. 
figs. 6-11). 
Branching normally in one plane. Stem strong, oval in trans- 
verse section, the longest diameter being the lateral one. Mode of 
branching normally dichotomous combined with pinnation. Distance 
between points of origin of main branches considerable, but sides of 
branches occupied in these intervals by small branches or pinne, 
irregular in size and point of occurrence, occasionally found on the 
anterior surface ; branches of main system decreasing gradually in 
thickness to the extremity of the corallum, somewhat tortuous, 
decidedly compressed from front to back in most places, the lateral 
diameter being to the antero-posterior about 11:9; pinne short, 
coming rapidly to a point, circular (or almost so) in transverse 
section, generally curved or tortuous, and not exceeding 20 mm. in 
length. Axis of corallum hard, not easily indented with a knife, 
solid; in main stem, and for a considerable distance up the main 
branches, of a deep crimson-red colour with a tinge of scarlet, 
resembling the colour of dried salmon’s flesh ; in the upper branches 
and the pinnee the central portion of the axis becomes paler, being 
at first pink and finally white, this axial pale tract widening as it 
approaches the extremity of the branches or pinnz, the axes of 
whose apices are white throughout. Surface of hard axis very 
finely striated in the longitudinal direction, with about five striz to 
1 mm., more deeply striated on smaller branches and pinnz ; surface 
otherwise even, with the exception of a tendency to roughness at the 
ends of the pinna, and very slight (almost imperceptible) shallow 
depressions beneath the calicles. Cortex about *3 mm. in thickness, 
completely concealing all inequalities of the axis, except at ends of 
pinne; friable, of a pale vermilion colour ; posterior and lateral 
surfaces even, and devoid of verrucae, with the exception of a few 
scattered ones on and near the stem and at the ends of some pinnee ; 
anterior surface beset with verrucz at intervals of 1 to 3 mm., and 
with minute punctiform elevations, visible only by the aid of a lens, 
uniformly distributed over the intermediate spaces to the number of 
about 25 in a square millimetre. Verrucze broad, truncate above, 
rising abruptly from surface; of same colour as the general cortex ; 
in retraction they may be completely closed; wrinkles between the 
8 valves generally obsolete or very slight in the retracted state; dia- 
meter of verrucz 1 to 1:25 mm., projection from cortex about °5 mm. 
Spicules of cortex of two kinds, viz. :—(i.) Cylindrical, sexradiate, 
colourless, with short thick axis; at each extremity two tubercles 
project from the side of the shaft (which does not project beyond 
them), at right angles to it; on each of the anterior and posterior 
aspects of the spicule (reckoning those which bear the above-mentioned 
four tubercles as the lateral ones) one tubercle is set at right angles 
to the long axis of the shaft, near its extremity, but at opposite ends 
