Bittium parcum (Gould, 1861). (Synonym: Bittium hawaiienses Pilsbry and Vanatta, 1905.) Length, 3.5 mm; diameter, 1.5 mm. Shell: conic, turreted; spirally striate; dark brown to cream. Spire: protoconch of one and one-half shining buff whorls; teleoconch of five somewhat convex whorls; suture impressed. Sculpture: apical whorls distinctly keeled at the sutures with fine spiral striae between the keels; abapical whorls with somewhat sinuous and variously developed butresslike axial ribs crossed by fine spiral striae; a single varix on each whorl. Aperture: ovate; outer lip evenly arcuate; siphonal notch sharp, deep, and flaring. Color: variable — cream with opaque spirals; cream with dark brown spirals; or dark brown. These cerithids are among the most abundant of all mollusks in tide pools and on solution benches and reefs, occurring by the thousands on algae such as Valonia, Boodlea, Microdictyon, and Padina. Development is direct, the juveniles emerging from gelatinous egg masses deposited on algae and rubble.
B. parcum was described from the Ryukyu Islands.