Apart from the rarity and beauty of some of the denizens of the reefs, there are others that are singular and interesting, and some whose intimate acquaintance is quite undesirable, save from a scientific and safe standpoint. A miniature marine porcupine decorates its slender spines of white with lilac tips, sharp as needles, brittle as spun glass, and charged with an irritant which sets all the nerves tingling. On the reefs uncouth fish pass solitary, isolated lives, in hollows and crevices of the coral, sealed up as are the malodorous hermits in rocky cells at Lhassa, and dependent for doles upon the profuse and kindly sea. Their bodies seem to mould themselves roughly to the shape of the hollows to which each has grown accustomed as crude but almost inanimate castings. To obtain perfect specimens the mould must be shattered. If the body does not yet fill the hollow, the inhabitant clings desperately to it, wedging itself with wonderful plasticity into odd corners and against niches, resisting to the last efforts at eviction. Torn from its home the fish is a feeble, helpless creature, incapable of taking care of itself, quite unfit to be at large, though apparently belonging to the self-reliant shark family. More than one species of fish, it is said, inhabit these coral grottoes. A compact creature with prominent rodent teeth ejects a spurt of water when its retreat is approached at low tide, while about its front and only door are strewn (after the manner of the "bones, blood and ashes" of the two giants in the valley through which Christian of THE PILGRIM'S PROGRESS passed) the shells of the crustaceans and molluscs it has devoured.