On a single spray of ruddy Gorgonia several of these commensal molluscs may occur in various stages of development--the smaller no bigger than the wing of a fly and almost as frail, the larger three and four inches long, and each whatsoever its proportions securely budded on and growing from a spur, while frequently the valves of the large are bossed with limpets and other encumbrances. In appearance the shell represents a deformity in usurpation of a thin pencilate "growth" of coral a foot long, for the exterior colouration is that of the coral. Quite independent of their host for existence, these molluscs are not to be stigmatised as parasites, though the individual spur to which each is attached is invariably destroyed by the union, merely sufficient remaining for the support of the intruder. Natural science provides many illustrations of symbiosis, or the intimate association of two distinct organisms. This example may be out of the common, and therefore worthy of inclusion in a general reference to the life of the coral reef. A third species, rare in a certain sense only, is of a most retiring, not to say secretive, disposition. For several years I sought in vain a living specimen of a flattened elongated bivalve (VALSELLA), buff-coloured externally, very lustrous within, with a hinge the centre of which resembles a split pearl. The blacks could offer no information beyond that which was delightfully indefinite. "That fella plenty alonga reef. You look out. B'mbi might you catch 'em!" "Tom," who never wilfully parades his ignorance, boldly asserted that they favoured rocks, but he had no name for them, and no living specimen was ever forthcoming to substantiate confident opinions.