Dillwynella modesta is a species of sea snail, a marine gastropod mollusk in the family Skeneidae.

The smooth, whitish shell is covered with an extremely thin epidermis which rises in microscopic blisters.

The sculpture shows faint lines of growth except on the base where a single rounded riblet or carina bounds a somewhat concave lunate space outside of the polished columella.

The thin, sharp outer lip has a moderate callus on the body.

[3] This marine species occurs off St Lucia, Caribbean Sea, at depths between 413 m and 805 m; in the Atlantic Ocean off southeastern Brazil.