Body oval, depth 44% of length, compressed; small pointed head; no hump before eyes; mouth is small, horizontal and opens at the front; top jaw relatively long, reaching under pupil; the top jawbone slips partially under the under-eye bone when the mouth is closed; teeth immovable incisiform, bases set horizontally in mouth, rounded tips and a curved, hockey-stick shape; teeth on center of roof of mouth and on tongue; dorsal fin continuous, XI, 11, spines that fold down into a scaly groove, front rays of soft dorsal fin relatively high; anal rays III, 11, soft fin moderately high at front; tail fin forked; paired fins are relatively short; origin of the pelvics behind the base of the pectoral fin; scales small, thick and rough, covering the body, head (except forward of eyes) and soft portions of the median fins; scales in oblique series just below lateral line 62-72.
Color variable: dark-phase fish are uniform light grey with faint dark stripes along scale rows of flanks, opercle and lower jaw silvery, tips of jaws dusky, fins pale; yellow-phase individuals are entirely bright lemon yellow, with a dark eye; other individuals are dark variably blotched with yellow.
Size: reaches 40 cm.
Habitat: shallow rocky reefs.
Depth: 0-20 m.
Apparently restricted to the Revillagigedo Islands.