Proneptunea subfenestra is a species of sea snail, a marine gastropod mollusk in the family Prosiphonidae, the true whelks.
References
Oliver P.G. & Picken G.B. (1984). Prosobranch gastropods from Signy Island, Antarctica: Buccinacea and Muricacea. British Antarctic Survey Bulletin. 62: 95–115. Engl, W. (2012). Shells of Antarctica. Hackenheim: Conchbooks. 402 pp.