Shell high-spired, about three times as long as wide, of 9-11 whorls. Sculpture on spire whorls of a spiral row of knobs forming a very weak keel on the mid-whorl, fine spiral cords adapically between this and the suture, and coarser, granulose spiral cords on the abapical part and on body whorl. Body whorl somewhat constricted, usually with a poorly developed varix. A short, narrow and deeply impressed siphonal canal.
whitish with an irregular pattern of dark brown flames and mottles, interrupted on the spiral row of knobs.
common size :
C. egenum is a rather featureless cerithid species, but may be distinguished from the smaller native species of Cerithium by the sculpture of the spiral cords, which are shiny and granulose, and by the more closed siphonal canal.
BIOLOGY / ECOLOGY
The protoconch of 2.5 whorls (usually eroded in the adult) indicates planktotrophic larval phase (Houbrick, 1992).
in the Indo-Pacific, this species lives in sand pockets of intertidal or very shallow pools of rocky shores.