Genus Cerithium is a member of a diverse group of shells characterized by having an elongate, high-spired shell ornamented by many spiral ribs and crossed by varices (= groups of swollen axial ribs). The aperture is smooth interiorly and has a distinctive frilled margin and a slightly reflected (strongly bent) anterior canal.
The genus Cerithium has a geologic record of Late Cretaceous to present day. There are many Cenozoic species and most of these were shallow-water dwellers that lived mostly intertidally in tropical waters (Houbrick, 1992).
One of the extant (living) species of Cerithium is Cerithium nodulosum, which has a fossil record extending back to the late Miocene. Today, this species is commonly found immediately shoreward of reef edges, as well as on intertidal rocky shelves, having veneered sand, as well as shallow, sandy depressions. It is found today only in the Indo-Pacific region. For example, it occurs along tropical continental shorelines and among island groups throughout the Red Sea and Indian Ocean, including East Africa and Mozambique. It is found throughout SE Asia, Indonesia, and the tropical part of Australia. In the Pacific, it ranges from near Japan throughout Melanesia, Micronesia, and Samoa (Houbrick, 1992).
Apertural and abapertural views of a Recent specimen of Cerithium nodulosum, height 4 inches (= about 10 cm), collected in shallow water from Okinawa in the western Pacific Ocean. The white-circular area on the apertural view is a small-sized encrusting oyster.
Note: When I look at specimens of C. nodulosum, I am immediately reminded of the abundant cerithid shells that I have seen in certain Eocene beds in the Paris Basin region of France.
Reference Cited
Houbrick, R. S. 1992. Monograph of the genus Cerithium Bruguiere in the Indo-Pacific (Cerithiidae: Prosobranchia). Smithsonian Contributions to Zoology, number 510.
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