Risella Gray, 1842 Bembicium is a genus of sea snails, marine gastropod mollusks in the family Littorinidae, the winkles or periwinkles.

[1] (Described as Risella) The depressed shell is trochiform, with flattened whorls and a keeled periphery.

The aperture is rhomboidal, marked with brown inside the margin.

These shells are distinguished from Trochus, which they resemble in form and sculpture, by their non-nacreous interior.

The animal is distinguished by eyes on the tentacles instead of on peduncles, and by the absence of the lateral membranes of the foot.