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Show MR. CYRIL CROSSLAND ON THE [Mar. 7, (5) Echirioderms.-Boring Echinids (Echinometra subangularis) occur all round the coasts in enormous numbers, in shallow pools of the shore-platform; the holes are generally drilled as near together as is possible. Just below the steep incrustation-belt they occur again in the same profusion, but in the belt itself are much rarer, except where it is horizontal. It is very remarkable that this form produces equally conspicuous effects upon rock of all degrees of hardness, whether nullipore, coral, sandstone, or the very hard black basaltic rock. But the total result of their destructive action is small, e. g. on sandstone of the St. Yincent reef amounting to the deepening of shallow pools by three or four inches. Indeed in many cases the Echinid merely takes advantage of the peculiar " potholed " forms the calcareous rocks assume under the influence of the sea and does no drilling at all. In any case as soon as shelter is obtained drilling-operations cease, and naturally sheltered crevices show feeble, merely adaptive traces of this action. On exposed surfaces as soon as the recess is made deep enough for shelter the action ceases, though several generations of Echini occupy the same place, as is shown by the fact that the size of the hole has often no relation to that of its occupant, full-grown Echini frequently occupying extremely shallow depressions and in other cases a young specimen, an inch or so across, being in possession of a full-sized hole, 3 inches in diameter and depth. But on growing Ooral the action is more important. Whenever a colony comes to overhang a burrow it is eaten away and this portion killed, as though semicircular canals had been gouged out in a line with the edge of the burrow beneath. In this way pools which would be full of coral possess but stunted remnants, and the extent of coral-growth on these coasts is very greatly reduced. It should be noted that these are not the only borers the instincts of which may be satisfied by an accidental crevice. I have found even so highly specialised a borer as the Polych?ete Eunice siciliensis inhabiting natural crevices in the nullipore and Serpulid combination. 5. T h e St. Y in c e n t F r in g in g -R e e f . Although true " coral-reefs " are absent from these seas, a remarkable simulacrum of a nullipore fringing-reef exists immediately to the south of the town of St. Yincent. The Admiralty chart gives a much larger structure than that at present in existence. In fact, there have been two distinct though perfectly similar reefs, the northern and broader having been now completely removed to make room for the piers &c. of the Coaling Companies. The two reefs were separated by lava rock at the base of a volcanic hill, 100 feet high, on the shore, the importance of which will appeal- later. The surface of the reef is at a level of from one to two feet above that of lowest tides, on the whole flat, with shallow pools, |