The most gorgeous denizen of these waters is likewise one of the most curious—­a fish resembling the surf parrot fish (PSEUDOSCARUS RIVULATUS), but seeming to surpass even that brilliant creature in colouring.  It subsists on limpets and may be seen, a lustrous blue, at half tide feeding in favourite localities.  The shape of the head and shoulders reveals something of the character of the fish, though the purpose of its resplendent appearance may not be obvious.  Both head and jaws typify strength and leverage power.  The mouth resembles the beak of a turtle or rather that of a balloon fish (TETRAODON).  The under jaw protrudes slightly, and is fitted (in the case of the male) with two prominent canine teeth; the upper jaw has also a pair of projecting teeth of similar character.  Each of the jaws consists of two loosely sutured segments, the articulation of the lower being much the freer.  The gullet is horny and rasp-like, and in its exterior opening is an auxiliary set of teeth of most remarkable formation.  The upper part of this interior set in some respect resembles the under jaws of a land animal, but there are marked distinctions.  It consists of two bony structures, slightly curved outwards, lying parallel to each other and bound together by tough ligaments which not only permit a certain amount of independent lateral movement, but also independent action forwards and backwards.  Each of the structures is fitted with a dozen to sixteen closely packed teeth, and at the rear of each is a magazine charged with five or six more, ready to move up and forward into position for active service as those ahead are worn away.  The principle of modern magazine rifles is surprisingly exemplified by these reserve teeth.  The lower jaw or rather dental plate resembles a flattened palate; the whole surface being studded with teeth, the edges of which overlap.  It may be described as a piece of mosaic work in white and ivory.  There are between sixty and seventy teeth resembling incisors on the dental plate.  The whole seem to be in a state of perennial renewal to compensate for wear and tear.  As those of the front row are broken or worn down, the next succeeding row occupies the frontal position.  The teeth are deeply set in the bony base of the inverted palate, or rather obtrude but slightly above the surface, their office being to break down and grind to powder flinty food.

The outward and visible teeth of the male are apparently given as weapons of defence, since they do not occur in the female, which has four back teeth.  From their prominent position the teeth of the male must also be used for grasping and levering or pulling steadfast limpets from rocks.  They needs must be hard and have strength as well as science at the back of them, for a limpet can resist a pulling force of nearly 2000 times its own weight.  The sutures of the jaws of the fish enable it to accommodate its grip to the various sizes of limpets, and to take a fair