Elongate, compressed, tapering body; large bulbous head; eye large, high; no cirrus at front nostril; end of top jaw straight, without fringe at rear; upper jaw 51-53% of head length, same size in males and females; lips with inner papillae; center of roof of mouth without teeth; no broad flap under operculum; gill rakers 34-35; dorsal rays XI, 13-14; anal rays II, 13-14; pectoral rays 18 (rarely 17); tail rounded, much shorter than head; lateral line on front half of body only, high; scales small, smooth, none on head, body with 65-70 oblique scale rows.
Females and non-courting males with orange-brown head and dark brown to blackish body, covered with relatively large blue spots; courting males white anteriorly and blackish on posterior half with large brown spot on anterior part of dorsal fin; no obvious color inside mouth; small juveniles yellow with blue spots.
Maximum size about 10 cm.
Habitat: found in sandy rubble areas in colonies of up to several hundred fish with a minimal spacing of about 1m between individuals; each fish constructs a lid over their burrow entrance at dusk and rebuilds the opening each morning.
Depth: 5-25 m.
The lower 3/4 of the Gulf of California and the Revillagigedo Islands.