Diagnosis: adipose fin always present; posterior nostrils always closer to each other than anterior ones; 7-9 branched pelvic fin rays; nasal barbel at least reaching to midway between eye and opercle; posterior side (inner side) of pectoral spine feebly serrated; swim-bladder with posterior caecum which extends caudally on one side of body (dextrally or sinistrally) to posterior end of anal fin (Ref. 43912).

Description: 12-14 branched pectoral fin rays; 55-61 branched anal fin rays, first 3-4 anal rays unbranched; pelvic fins with i + 7-9 soft rays; 53-54 non-fused vertebrae; 18-20 + 7-9 gill rakers on anterior branchial arch; 10-12 branchiostegal rays on one side of head; caudal peduncle deeper than long; nasal and outer mandibular barbels reaching at least to almost midway between eye and opercle and at maximum almost to posterior border of opercle; maxillary barbel rather well developed and always reaching beyond opercle, at maximum to end of pectoral spine; inner mandibular barbel reaches at least to middle of eye and at maximum to midway between eye and opercle; lower jaw reaching anteriorly to tip of snout or slightly projecting; head rounded and rather large; caudal caecum of swim-bladder, dextral or sinistral, extending to posterior end of base of anal fin between haemal spines and ventral muscles; in profile dorsum rises rather abruptly from flat head, forming a convexity between occiput and dorsal fin, progressively steeper and more convex from smaller to larger specimens; eyes lateral; teeth small, with points directed backwards; vomerine and palatine bands wider than premaxillary, distinct from each other but contiguous, palatine band may be divided into two groups (Ref. 43912). Probably most closely related to I. voltae from West Africa, from which it can be easily distinguished by the finely serrated inner side of the pectoral spine (Ref. 43912).

Coloration: Preserved specimens: sides pale with few indistinct fine lateral stripes; head and back somewhat darker; in smaller specimens lateral stripes (one above and one below lateral line, one just above base of anal fin) somewhat more distinct; anal fin faintly speckled, other fins colourless (Ref. 43912).