Fossarus cumingii (A. Adams, 1855a). (Synonym: Fossarus ecphora Pilsbry, 1917.) Length, 3 mm; diameter, 1.5 mm. Shell: turbiniform, globose, thin; with fine spiral cords and threads on the last whorl; white. Spire: protoconch of two brown whorls, the apical with fine axial ribs, the abapical with a spiral keel crossed by
axial ribs and punctate spiral striae; teleoconch of four whorls, the apical whorls flattened and the last whorl much the largest. Sculpture: apical whorls with strong spiral keels becoming threadlike on the last whorl. Aperture: subcircular; umbilicus plicate. Color: white.
These animals are occasionally found under rocks or in crevices in tide pools; beach worn shells are common in drift.
No locality was designated in A. Adams's (1855b) description and the distribution of this species apart from its occurrence in Hawaiian waters is not known.
F. cumingii is distinguished from F. garrettii by its flatter spire and more weakly developed spiral sculpture.