Diagnosis: adipose fin present; position of nostrils slightly variable, distance between both anterior and posterior nostrils being approximately equal; lower jaw shorter than upper jaw and completely surrounded by upper lips when mouth is closed; inner side of pectoral spine feebly serrated; barbels very long; nasal barbel always reaching to posterior border of opercle or somewhat further, maxillary barbel at least reaching to end of pectoral spine and outer mental barbel reaching to midway along pectoral spine; colour pattern characterized by brown back and head, large dark (brown) stripe along lateral line and oblique brown stripe from below anterior part of lateral line to origin of anal fin (Ref. 43912).

Description: ii-iii + 38-44 anal fin rays; 40-41 non-fused vertebrae; 9 branchiostegal rays on one side of head; caudal peduncle somewhat deeper than long or slightly longer than deep; barbels very well developed, nasal barbel reaching just beyond head; maxillary barbel very long, sometimes reaching just beyond end of pectoral spine (when folded against body); outer mandibular barbel also reaches beyond head, almost to end of pectoral spine at maximum and inner mandibular barbel reaches to posterior border of eye (Ref. 43912). Schilbe zairensis is a peculiar species with a coloration characterized by a dark lateral line as in S. intermedius or as in some specimens of S. mandibularis and S. multitaeniatus; S. zairensis differs from S. intermedius by the lower jaw being shorter than the upper one, while it reaches slightly beyond the snout in S. intermedius; on the other hand an adipose fin seems always present in S. zairensis, while it is absent in numerous populations of S. intermedius especially those from occidental Africa; S. zairensis is distinguished from S. mandibularis and S. multitaeniatus by the very long barbels and by the configuration of the mouth, especially by the mutual position of both jaws; S. zairensis seems closely related to S. djeremi from the Sanaga Basin sharing with this latter species a similar gross morphology of the head, rather similar meristic characters, almost identical body proportions and a comparable coloration, however in S. djeremi the circumoral barbels are considerably shorter, the number of branched anal fin rays is slightly superior (44-51 versus 38-44 in S. zairensis) and the eye is somewhat larger (26,5-30,5 %HL versus 23,5-27,1 %HL in S. zairensis) (Ref. 43912).

Coloration: in alcohol: back and head brown; dark brown band along lateral line; broad dark line on belly from base of pectoral fin to anterior part of base of anal, this line indistinctly continues above base of anal as faint speckles; belly pale, fins generally uncoloured, base of caudal and dorsal fins being somewhat darker (Ref. 43912).