by Matthew Law

Cliona celata Grant 1826 is a sponge of the class Demospongiae, which is found in seas around the world. In life it forms large colonies and is readily recognisable by its bright yellow colouration. It is a boring sponge, found on limestone and other calcareous platforms such as shells. It is this latter characteristic that is of most interest to archaeologists, as shells of marine molluscs (particlulary the edible oyster Ostrea edulis L.) are often found with a series of holes bored by the sponge (see picture).This is usually a sign that the mollusc shell is derived from a fully marine environment, and not from farmed stock (Law 2007). Although common in British waters, Cliona celata is apparently absent from the North Sea (Picton and Morrow 2005)

Valve of edible oyster (Ostrea edulis) bored by Cliona celata (image copyright Matthew Law 2008)

Law, M., 2007: A Report on the Oyster Shell from Prior Park School, Cricklade. Unpublished Archive Report, Bristol and Region Archaeological Services.

Picton, B.E. & Morrow, C.C., 2005. [In] Encyclopedia of Marine Life of Britain and Ireland http://www.seaslug.org.uk/marinelife/species.asp?item=C3020

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