Acronuridæ.

Body compressed, oblong or elevated, covered with minute scales. Lateral line continuous; tail generally armed with one or more bony plates or spines, which are more developed with age, and frequently absent in very young individuals. Eye lateral, of moderate size. Mouth small; a single series of more or less compressed, sometimes denticulated, sometimes tapering incisors in each jaw; palate smooth. One dorsal fin, the spinous portion being the less developed; anal with two or three spines; ventral fins thoracic. Pseudobranchiæ well developed; air-bladder present, forked posteriorly. Intestines with more or less numerous circumvolutions.

Seas between the tropics. Herbivorous fishes.

Acanthurus triostegus. West coast.

——grammoptilus. North coast.

——triostegus. West coast.