Shell small, conical-fusiform, spire well raised, fairly solid. Colour (dead) whitish-brown, with a white protoconch. Whorls 6, turreted, regularly increasing. Protoconch large, white, the first whorl and a half smooth, then closely-set longitudinal riblets are seen, and the whorl becomes carinate. The remaining whorls are acutely carinate, with an area below the suture, either smooth or with arcuate striae: below the carina appear numerous longitudinal riblets, decussated by spiral carinations, giving the shell a somewhat prickly or nodulous appearance. The mouth is small, with a well-marked sinuation above; columella vertical, a little twisted at the base. Long. 5, lat. 2.5mm.

Type locality: PORCUPINE st 17, 39°42N, 09°43W, 1980 m. Material examined: the type material. Distribution. Only known from the type locality.
Remarks. D. megalacme can be distinguished from D. pruina by having direct development and stronger axial sculpture below the main keel.