Cerithium strictum: Shell narrow, elongate, tapering in a slender spire and blunt anteriorly. Colour white, irregularly longitudinally splashed with chestnut. Whorls seven, the upper angled, the last straight. Sculpture: round the angle of the upper whorls runs a line of tubercles, of which eleven occur on the penultimate. Very slight longitudinal undulations, hardly to be called ribs, extend from these tubercles across the whorl ; both vanish before attaining the last whorl. This latter is girt with about twenty, sharp, revolving ridges, of which the central is largest and corresponds to the tuberculated angle of the earlier whorls ; the rest vary in size and spacing, the basal ridges being least and closest; the upper seven ascend the spire. A large varix is behind the aperture, and a weaker one half a whorl back, none else appear. Aperture perpendicular, oval. Outer lip smooth within, sharp edged, crenulate outside, inner lip excavate, thickly lined with callus, with a posterior nodule at the margin of the channelled angle. Length 7, breadth 3 mm.

Cerithium egenum Gould, 1849. Length, 8 mm; diameter, 3 mm. Shell: conic-slender; with obscurely beaded spiral threads; cream splashed with dark brown at the base of the last whorl. Spire: protoconch of three and one-half ovate whorls, the apical one and one-half whorls smooth and white, the abapical whorls brown, axially ribbed from the suture and with two keels; teleoconch of eight barely convex whorls; suture indistinct. Sculpture: each whorl with a large, granular spiral about the center, remainder of whorl with spiral threads; with occasional axial varices. Aperture: ovate; outer lip thick; siphonal canal short, not recurved. Color: cream with a splash of dark brown on each whorl, the last whorl with a dark band below the periphery and extending over the outer lip. These cerithids are occasionally found buried in sand in tide pools and on benches, sometimes with C. atromarginatum. The veligers are bilobed; they metamorphose when three to three and one-quarter whorls are complete, at a length of 500 µm (J. B. Taylor, 1975). C. egenum ranges throughout the Indo-West Pacific from the Red Sea and Cocos-Keeling Islands (Maes, 1967) to the Marshall and Society Islands. C. egenum is distinguished from C. atromarginatum by its slender shape, distinctive color pattern, and larger protoconch.