| OCR Text |
Show 1899.] CORALLIID^E O P M A D E I R A . 59 The spicula of the cortex comprise three forms :-(1) Spicules shaped like an opera-glass or like two carafes joined at the sides and having two necks ; the bodies are coarsely tuberculated and the ends of the necks are set with a cycle of conical tubercles. (2) Small, cylindrical, stout with two whorls, each of four thick rays, on the shaft at right angles thereto ; the projecting ends of the shaft with the two whorls of rays make up a ten-rayed spicule; the ends of all the rays are tuberculated. (3) Numerous irregularly formed spicules which may be compared to balls with several thick rays : they seem allied to the last form, but neither axial shaft nor whorls of rays can be made out. In addition to these forms the polype-cells yield (4) numerous monaxile spicules about one and a half times the length of the spicule (2); some are cylindrical, others fusiform or clavate, and all are more or less tuberculated ; (5) a few cruciform spicula varied in form and usually imperfect, but consisting essentially of four tapering arms at right angles to each other, their bases meeting at the centre with equal acute angles. (The spicula are figured on Plate VII. fig. 3.) This species is less robust than the other two here described, so far as can be judged from the few known specimens. Three examples have been obtained at Madeira at different times, but for many years no others have occurred. The largest specimen was presented to the British Museum, and a second, smaller, but with perfect cells, was given to the Liverpool Museum. With these two specimens before him, Dr. Gray (P. Z. S. 1867, p. 126) assigned the latter to his Hemicorallium johnsoni, saying it was evidently the same species and showed the coral in its young state. His paper is illustrated by a good woodcut (here reproduced, seep. 58), which displays the entire specimen and the polype-cells. The cells are unfortunately very fragile, and drop off from the dry coral at the slightest touch or jar. The specimen in the British Museum is without its base; it has a height of 170 millim. (6f in.) and the branches have a spread of about the same. The stem below the branches has a diameter of 6 millim. There are four principal branches, which in their lower parts vary in thickness from 4 to 7 millim.; above, they taper gradually and throw off tertiary and quaternary branchlets, which are seen to end in sharp points where stripped of the cortex. Two of the branches were quite dead long before the coral came from the sea, as was shown by the number of the plant-like polypiaries of hydroid zoophytes attached to them. The branches are often curiously perforated and tunnelled longitudinally on their anterior faces, and at these places are thicker than elsewhere. Boring animals appear to have attacked them, and it would seem as if fresh stony matter had been secreted so as to cover over the passages which are open at both ends, and the longer ones have usually a series of large openings at the sides. Sometimes a portion of the branch itself has been removed ; at other places the stony axis does not appear to have suffered. One tunnel measured 35 millim. in length and had eleven openings at one side. |
