Diagnosis: rather small, no specimen larger than 25 TL known (Ref. 78218). 38-43 (Ref. 78218) or 39-43 (Ref. 34006) vertebrae. Narrower head, mouth and oral tooth bands than M. electricus; body with moderately large scattered black spots; narrow pale bars on anterior part of caudal peduncle and caudal fin base; caudal and anal fins darkened centrally, with sharply defined pale margins; may attain 300 mm (Ref. 34006).

Description: 8-9 anal fin rays (Ref. 78218).

Coloration: body grey, darker on upper part and light on belly; scattered dark dots the size of the eye or smaller; juveniles have black stripe across caudal peduncle; proximal half of caudal fin white, followed by half-moon-shaped spot and white edge to the fin; white band runs from posterior half of adipose fin to anal fin; in front of this a dark saddle-like spot extends across body and anterior half of adipose fin, becoming broader from flanks upwards (Ref. 78218).