Bullia laevissima, common name the fat plough shell, is a species of sea snail, a marine gastropod mollusk in the family Nassariidae, the Nassa mud snails or dog whelks.

Externally, near the base, is observed a prominent fold, which is continued winding round as far as the inferior third of the columella.

According to the observations of Quoy and Gaimard, the animal of this species is blind; and what renders it particularly remarkable, is a very large foot, extending from all parts of the shell.

This mollusk possesses the power of absorbing by its foot, by means of pores with which this part is provided, a large quantity of water, which it throws off again, when it is disturbed, in several directions.

It lives in deep water, and when it is brought towards the shore, its foot still farther enables it to bury itself in the sand.