Diagnosis: 8-13 gill rakers (exceptionally 7-14, Ref. 43912) on lower limb of first gill arch; 41-66 branched anal-fin rays; eyes positioned laterally (Ref. 43912, 57127, 81643). In the Nile (Ref. 43912) and in West Africa adipose fin usually absent, but specimens with a rudimentary adipose fin occasionally present (Ref. 43912, 57127, 81643). In Central and East Africa populations without as well as with entirely developed adipose fin occur; in several populations both morphotypes are mixed together, the adipose fin being absent or present but sometimes varying in size from a recognizable protrusion low down the back to a fully developed adipose fin; posterior nostrils always closer to each other than are anterior ones; lower jaw reaches beyond snout but hardly remarkable in some specimens, mouth being almost isognath; inner side of pectoral spine feebly serrated; nasal barbel at least reaching to midway between eye and opercle but often reaching beyond this level; small specimens (up to about 15 cm) with typical colour pattern with dark lateral bands along sides and anal fin, this pattern gradually disappearsing in larger specimens, the body becoming in general entirely brownish, yellowish and silvery with very few traces of dark lateral bands (Ref. 43912). Eyes positioned laterally (Ref. 81643).

Description: anal fin long, extending from vent almost to origin of caudal fin; 4 pairs of short, circum-oral barbels (Ref. 34290). 41-66 branched anal fin rays; 40-49 non-fused vertebrae; 7-14 gill rakers on lower part of anterior arch; 8-11 branchiostegal rays on one side of head; caudal peduncle generally deeper than long but in some cases as long as deep; length of circumoral barbels rather variable and showing negative allometry; nasal barbel reaches at least to midway between eye and opercle (large specimens) but at maximum just beyond anterior border of opercle; maxillary and outer mandibular barbels reach at least to midway between eye and opercle and at maximum to just beyond anterior border of opercle; inner mandibular barbels short and at maximum reach to just beyond posterior eye border; profile of head very variable, in general rather straight from snout to occiput but in many specimens straight only anteriorly, nape ascending very abruptly from occiput to origin of dorsal fin; snout morphology also rather variable: usually broad and round, but can also be more or less rectangular or rather narrow; inner side of pectoral spine and posterior side of dorsal spine feebly serrated (Ref. 43912). Specimens without an adipose fin are very similar to S. uranoscopus, which however has more numerous gill rakers on the lower part of the anterior arch (13-16 against 7-14 in S. intermedius) and more branched anal fin rays (59-73 against 41-66 in S. intermedius); specimens of S. intermedius with an adipose fin are very similar to S. moebiusii known from some East African coastal basins in Tanzania, but in the latter the nasal barbels are rather short, never reaching beyond the posterior eye border, a pronounced postoccipital hump is present and there is a fairly high number of branched anal fin rays (60-68 against an all over variation of 41-66 in all populations of S. intermedius)(Ref. 43912).

Coloration: live young individuals (to about 150 mm SL) with a peculiar colour pattern: head and back dark brown, with two brownish or blackish bands on sides, one along lateral line, other above anal-fin base (Ref. 43912, 57127, 81643). Two other dark bands above anal fin; dark stripe present along dorsal and ventral lobe of caudal fin (Ref. 43912). This colour pattern disappears with growth: head and back remain dark brown, but the lateral bands fade progressively and the sides become more or less whitish or silvery (Ref. 43912, 57127, 81643). Congo basin specimens sometimes with a somewhat mottled colour pattern (Ref. 43912). Preserved specimens: silvery colour of the body disappears almost completely (Ref. 57127, 81643).