Diagnosis: head depressed (Ref. 13337, 52193). Body elongated (Ref. 2915, 13337, 52193), shallow (Ref. 28714), ratio standard length/body depth 4.9-7.5 (Ref. 81274). Mouth large (Ref. 13337, 52193) and terminal (Ref. 13337, 28714, 52193, 81274), with 16-28 teeth in upper, and 14-28 in lower jaw (the number of teeth increases with size) (Ref. 81274). Chin (mental swelling) absent (Ref. 52193). Origin of dorsal fin behind origin of anal fin, nearer caudal fin base than tip of snout (Ref. 4903, 52193). Dorsal fin shorter than anal fin; mouth width subequal to snout length (Ref. 52193). Snout long (Ref. 52193), rounded, its length 1/5-1/4 that of the head (Ref. 4903), almost as broad as head (Ref. 2915, 81274). 21-33 dorsal- and 38-50 anal-fin rays (Ref. 52193, 81274). Head 3.4-5.1 times in standard length; interorbital space relatively broad, ratio head length/interorbital width 2.9-6.8; wide ranges for most of the meristic characters are caused by the existence of geographical clines (Ref. 2915, 81274).

Description: scales small; head and body elongated; median fins set well back (Ref. 52193). Caudal fin relatively small, forked with rounded lobes (Ref. 4903, 52193) and almost completely covered with small scales (Ref. 4903). Head smooth and depressed in front; mouth terminal with small pointed teeth in a single row (Ref. 52193). Teeth notched or slender and conical (Ref. 4903). Eye small (Ref. 52193), its diameter 2.5-3 times length of snout (Ref. 4903). Gill slit restricted to sides, inclined at an angle (Ref. 52193). Caudal peduncle nearly twice as long as deep (Ref. 4903).

Coloration: ground color dark bluish-grey, mauve or blackish, belly a little lighter (Ref. 81274), silvery white below, often with a bronze or yellow sheen (Ref. 52193). Juveniles with more intense coloration (Ref. 81274), darker, greyish blue or brown (Ref. 52193). Preserved specimens olive or greyish-brown above, whitish below (Ref. 4903).