Shell small (up to 35.5 mm), whitish to light brownish, fusiform, 7 or 8 convex whorls with sub-sutural concavity. Upper whorls slightly bicarinate. Diameter of upper whorls increasing more rapidly than lower ones.
Protoconch whitish, consisting of 1,25 whorls. Upper part smooth and glossy, last part (about 1/4 to 1/2 whorl) sculptured with some narrow but strong axial riblets. 0.7-1.0 mm in diameter.
Axial ribs traversing from suture to suture on upper whorls, withdrawing from upper suture on latter whorls. 9-12 rather weak, narrow ribs on 2 uppermost teleoconch whorls, separated by conspicuously narrow interspaces. 10-14 ribs on following 2 or 3 whorls, latter whorls usually without ribs. Large adult specimens sometimes with conspicuously strong axial knobs on body whorl.
Teleoconch begins with 4 spiral cords. 2 adapical ones clearly stronger from beginning and forming a weak, inconspicuous double keel on upper whorls, fading away on latter whorls. From second or third postnuclear whorl on, a fine intercalated thread appears between each pair of primary cords. Number of fine threads increasing up to 2 by intercalation on latter whorls. Rather weak spiral sculpture crossed by prominent axial growth lines giving surface the texture of linen.
Aperture ovate, whitish, pointed at both ends. Outer Up slightly crenulated, simple. About 18 rather fine internal lirae. Inner lip smooth, parietal callus thin, columellar folds absent. Siphonal canal shorter than aperture, slightly curved.
Periostracum light brown, rather thin.
Operculum corneous, brownish, typical of genus, shape and size corresponding to aperture, with terminal nucleus.
Radula typical of genus. Central tooth small, short. Base convex, broad, with 3 prominent cusps of about equal size projecting below base; top narrow, concave; both sides strongly convex. Lateral teeth curved, having 6 or 7 short pointed cusps of about equal size and a small pointed denticle at both ends.

F. riscus differs in being smaller, having less convex whorls, a clearly smaller number of much broader axial ribs with broader interspaces on upper whorls, an axially ribbed penultimate and body whorl and differences in radula morphology (clearly larger, elongate central tooth, a smaller number of much longer cusps on lateral teeth) and a different protoconch (only one whorl, sculptured with fine axial growth lines and 2 or 3 weak spiral threads on final part).
F. cadus differs in the less numerous and broader axial ribs, less convex whorls, the upper whorls increasing in diameter slower than in F. alisae, the last part of the protoconch is smooth or has some fine axial riblets, and has a different radula morphology (lateral teeth with less numerous but much longer cusps).

North of New Caledonia and Coral Sea, Chesterfield Islands, between 300 and 545 m deep.