Basilissopsis oxytropis is a species of extremely small deep water sea snail, a marine gastropod mollusk in the family Seguenziidae.

There are many not close-set, flexuous, longitudinal ribs above the periphery, but on the base merely lines of growth.

The apex is small and flat, the smooth embryonic 11⁄4 whorl hardly rising at all.

The columella is perpendicular, with a strong rounded sinus, which corresponds to a swelling within the umbilicus.

The umbilicus is not large, but deep, funnel-shaped, with a puckered sharp edge.