This distinctive species is characterized by 1) fusiform shell attaining 3.5 mm in height, 2) conical protoconch of 2.5 smooth whorls, clearly demarcated from the teleoconch, 3) teleoconch whorls with narrow shoulder slope, meeting at adpressed sutures, 4) body whorl oval, about four-fifths of total height, the last part disjunct, 5) aperture oval, subangular adapically, 6) sculpture of faint axial folds and overriding spiral cords and threads; the axials tend to fade away over the base.

DISTRIBUTION AND HABITAT. Macromphalus thelacme was previously known from the Eastern Indian Ocean. According to BOSCH et al, (1995), it is an eurybathyic species thriving in both shallow and deep water. Except for this, there is no other information about its ecological requirements.