Cerithidium perparvulum (Watson, 1886). Length, 2 mm; diameter, 0.75 mm. Shell: conic-elongate, turreted; with finely beaded axial ribs and spiral threads; white to brown. Spire: protoconch of two smooth, white or brown mamillate whorls; teleoconch of five convex, slightly turreted whorls; suture impressed. Sculpture: straight axial ribs with interspaces of about equal diameter and spiral threads rendering the ribs nodulose where they cross. Aperture: subcircular; outer lip thin, smooth; columella straight; siphonal canal abruptly short. Color: variable — white, cream, yellow, or brown.
These shells are occasionally found in tide pools and on fringing reefs but are abundant at depths of 13 to 50 m where they form the dominant element in the micromolluscan assemblages, comprising up to 25 percent of the small gastropods found. The planktonic veliger larvae are among the most common cerithiaceans in the Hawaiian plankton. These dialids deposit their first egg masses when the shell has nine or ten whorls; when food is plentiful in the laboratory they pass from newly settled juveniles to reproductive adults in less than one month (J. B. Taylor, 1975).
C. perparvulum was described from the Torres Straits and Cape York, Australia, Tonga, and Honolulu.