Fluxinella marginata is a species of extremely small deep water sea snail, a marine gastropod mollusc in the family Seguenziidae.

The thin, whitish shell is very depressed, conic, and sharply keeled at the periphery, The 5 teleoconch whorls are spirally divided into 2 parts, convex above but concave if taken as a whole.

This marginal part is sculptured by rather conspicuous spiral and stronger, oblique, but nearly straight, riblike radiating striae, which on the upper part make the keel slightly crenulate (on the largest specimen the keel is smooth, on account of the less conspicuous sculpture).

The margin is separated from the central part by a deep groove, with about 7 spirals and faint growth striae.

The umbilicus is large, pervious, scalar, and bordered by a strong rib which is surrounded by a deep groove, The umbilical wall is perpendicular.