Euchelus atratus, common name the blackish margarite, is a species of sea snail, a marine gastropod mollusk in the family Chilodontaidae.

Its color is black, brown, or grayish-pink, either unicolored or tessellated with dark spots.

The convex body whorl is rounded, quite abruptly and decidedly descending at the aperture.

are paler, and have a small riblet developed in each interstice, thus about doubling the number of spirals.

[4] This species occurs in the Red Sea and in the Indian Ocean off the Mascarene Basin.