The appearance and activities of the creature are such as to establish the delusion that it is not altogether amicable in its attitude towards even such a bumptious and authoritative product of Nature as man. Its agitated demonstrations--whatever their vital purpose may be--to the superficial observer are danger signals, a means of self-preservation, as a substitute for the hard calcareous armour bestowed upon other molluscs. The fussy red rays may impose upon enemies a sense of discretion which constrains them to avoid the lima, which, though hostile in appearance, is one of the mildest of creatures. The tentacles, too, have a certain sort of independence, for they occasionally separate themselves from the animal upon the touch of man, adhering to the fingers, while maintaining harmonic action, just as the tip of a lizard's tail wriggles and squirms after severance. Most of the blocks of submerged, denuded coral are the homes of certain species of burrowing molluscs, the most notable of which are the "date mussels" (LITHOPHAGA). The adult of that designated L. TERES is over two inches long and half an inch in diameter; glossy black, with the surface delicately sculptured in wavy lines; the interior nacreous, with a bluish tinge. This excavates a perfectly cylindrical tunnel, upon the sides of which are exposed the stellar structure of the coral. A closely related species (STRAMINEA), slightly longer, and generally of smooth exterior, partially coated with plaster, muddy grey in colour, adds to the comfort and security of existence by lining its tunnel with a smooth material, a distinction which cannot fail to impress the observer. In each case the mollusc is a loose fit in its burrow, having ample room for rotation, but the aperture of the latter is what is known as a cassinian oval, and generally projects slightly above the surface of the coral.