Body thin, oval in shape, with relatively long dorsal and anal fins and a slightly crescent tail. Body bluish gray to dark brown, and pale or darken dramatically (A. chirurgus dark phase). Body with 10 to 12 body bars, although they may be faint. Several markings radiate from the eye. Dorsal, anal and tail fins with blue or white borders. Base of tail with a sharp spine (like a surgeon's scalpel), sometimes with a white band behind the spine.
Size up to 35 cm.
Inhabits shallow reefs or rocky areas, down to 25 m. Often in loose aggregations. Mainly diurnal. Ingests sand when feeding algae. The sharp spines at both sides of the base tail are used as defensive weapons by slashing their tails from side to side. When not in use, they are folded backwards against the body.
Abundant to common Florida and Bahamas, common to occasional Caribbean.