Cerithidium diplax (Watson, 1886). Length, 2 mm; diameter, 1 mm. Shell: conic-elongate, slender; with two beaded spiral threads; transparent white or cream. Spire: apex attenuate; protoconch of one and one-half smooth whorls; tele¬oconch of six convex, turreted whorls; suture broad, shallow, impressed. Sculpture: the two apical whorls spirally striate, the others bicarinate with a larger and a smaller beaded spiral thread just below the periphery of each whorl. Aperture: subcircular; outer lip thin. Color: transparent, shining white or cream. Shells are found in sediments at depths of about 13 m and become very common in deeper waters at depths to 60 m. There is a planktonic veliger larva.
C. diplax was described from Amboina and has also been recorded from the Cocos-Keeling Islands (Maes, 1967).