ELEOTRIDAE Butis koilomatodon, 5.5 cm SL (photo by Ukkrit Satapoomin) Butis koilomatodon, 6.3 cm SL (from Nah Trang, Vietnam; photo by Seishi Kimura) Butis koilomatodon (Bleeker, 1849) Mud Sleeper D VI+I, 8; A I, 8; P1 21-22; LR 25-28; Pred.S 11-15. Body relatively short, subcylindrical and compressed posteriorly. Head slightly depressed; bony interorbital serration around dorsal margin of eye; jaws large, extending posteriorly to below anterior margin of eye; lower jaw protruding beyond upper jaw. Pelvic fins widely separated. Cheek and operculum with ctenoid scales; no scales on interorbital area. Color: blackish brown, with indistinct 4-5 broad dusky oblique bands on body; anteroventral part of pectoral fin with a distinct black spot. Size: 7.5 cm. Distribution: Indo-West Pacific. Remarks: found in tidal estuaries. Carnivorous. Often marketed fresh.