Translated from Boulenger, 1902:
The body is heavily compressed, the back rounded. The body depth is included 3 times in the total length, the length of the head 4 2/3 times. The head is as high as long, with a strongly curved profile; the snout is rounded, as long as the eye, continuing beyond the mouth; mouth is small, its width 1/5 of the length of the head; the teeth are small and truncated, 5 in the upper jaw, 6 in the lower; internarine space is a little closer to the eye than the end of the snout; the lower nostril is at the lower edge of the eye; the diameter of the eye is included 4 1/2 times in the head length, nearly 2 times in the interocular width, which is very curved. The dorsal fin, with 28 rays, is nearly 3 times deeper anteriorly than posteriorly, starting above the fifth anal ray, and its base measures 2/3 of the distance that separates it from the head. Anal, the same form as dorsal, has 31 rays; it is closer to the base of the pelvic than to the base of the caudal. The pectoral is pointed and almost as long as the head; it much exceeds the base of the pelvic, whose length is half that of the head. The caudal fin, partly covered with scales, has long and pointed lobes. The caudal peduncle is nearly 3 times as long as tall and a little shorter than the head. 45 scales along the lateral line, 11/17 in transverse series on the body, 10/10 between the dorsal and the anal, 12 around the caudal peduncle.
Brownish; a darker vertical band, rather poorly defined, between the origin of the dorsal and that of the anal; the anterior half of the caudal peduncle dark brown.
This species, which must be placed between M. pulverulentus, Blgr., and M. plagiostoma, Blgr., is represented by a single specimen, collected at Monsembé for the British Museum by the Rev. JH Weeks.
Size: Total length: 140 millimeters.
EOD and electric organ: simple biphasic waveform, approx. 0.6-0.7 millseconds in total duration. Height of first phase, P1, approx. 1/3 total peak-to-peak height. EOD suggests electrocytes of type NPp.