Shells small, whitish, usually globose, with a wide umbilicus and a large aperture. Members of this family share a characteristic: each species bears, on the early whorls, a minute sculpture, specific, quite different to that of adult shells, and generally more strongly marked. Protoconch multispiral (2-4 whorls).
 

« Shell ovate, deeply and largely slitted; spire acuminated; whorls convex, decussate; last whorl ventricose, suture deep. Aperture semi-ovate; columellar margin straight, sharp, unobstructed, anteriorly expanded; the umbilical slit is elongated; labrum arched, sharp, entire. » – genus Couthouyia, synonym, in A. Adams: “On some new genera and species of Mollusca from Japan”, Annals and Magazine of Natural History ser. 3 vol. 5, London 1860, p. 410. Operculum paucispiral with nucleus in lateral position.
 

« Our species can be considered intermediate between the Vanikoro and the Fossarus, with both these genera having a common shape […]. In agreement with Tiberi, Petit, Jeffreys and Weinkauff, I find it good to leave it in the genus Fossarus, and only in the probable case that the animal and the operculum showed significant differences between ours and those of the Vanikoro, Lacuna and Fossarus would be justified the establishing of a special genus, which I would then like to name, because of its relatively large umbilicus, Megalomphalus. » – S. Brusina: “Saggio della malacologia Adriatica”, Bullettino Malacologico Italiano vol. IV, Pisa 1871, p. 9.
 

« Vanikorids with a tall, rissoiform shell sculptured by low sigmoid lamellae, narrow or no umbilicus and with a simple foot with epipodial folds but without posterior sucker. » – Warén & Bouchet: “A new species of Vanikoridae from the western Mediterranean, with remarks on the Northeast Atlantic species of the family”, Bollettino Malacologico vol. 24(5-8), Milano 1988, p. 93.