OCR Text |
Show 228 MR. S. O. RIDLEY ON THE CORALLIID^E. [Feb. 7, considerable depth at which this specimen was obtained, not being greater than that from which Corallium 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 transverse 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 pinna?, 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; pinna? short, coming rapidly to a point, circular (or almost so) in transverse section, generally curved or tortuous, and not exceeding 20 m m . 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 pinnae 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 pinna?, the axes of whose apices are white throughout. Surface of hard axis very finely striated in the longitudinal direction, with about five stria? to 1 mm., more deeply striated on smaller branches and pinna? ; 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 m m . in thickness, completely concealing all inequalities of the axis, except at ends of pinna?; 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 pinnae ; anterior surface beset with verrucae 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. Verrucae 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; diameter of verrucae 1 to 1*25 mm., projection from cortex about *5 m m. 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 bevond 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 |