This really was a find! Something I had never seen before and didn’t know existed. Tiny, fragile, and looking like mere shell fragments in the sand, the shells of Pandora’s Boxes are easily overlooked. I guess I only noticed them because they were all ‘mother of pearl’ and glinted in the light.
Pandora’s Box shells are strange. The thin and brittle shells measure no more than 30 millimetres in length. The right valve is almost completely flat and, in life, sits snuggly on top of and slightly recessed within the left valve – which in contrast is markedly convex.
The overall outline shape of the shells is crescent-like with the dorsal edges concave. The front end of the shell is rounded but the back end of the shell is truncated – almost as if a piece has been neatly snipped off. A full detailed description of all the parts and features would take a considerable time but there is an excellent description in Norman Tebble’s British Bivalve Seashells – A handbook for Identification published by HMSO 1966 ISBN 0 11 491401. This is out of print but second-hand copies are still around. (If anyone wants the full scientific description for the shell of this species without obtaining a copy of this book, please contact me).
You can also click here to download a pdf file of an early paper written by J. A. Allen in 1954 On structure and adaptations of Pandora inaequivalvis and P. pinna. Quarterly Journal of Microscopical Science, Vol. 95, part 4, pp 473 482.
The odd shape and the distinctive features displayed in the shell are related to its life habits. This bivalved mollusc is adapted for life on sand and muddy sand off the south and southwest coasts of the British Isles and off the Channel Islands and Isle of Man. It lives from very low water mark to medium depths – perhaps 20 metres. It can accur in great numbers on very sheltered shores. These shells photographed here and others like them were found at Studland Bay in Dorset, UK.
The mollusc has been recorded lying horizontally on the cupped left valve on the surface of the seabed with the flat right valve uppermost and forming a lid to the ‘box’. It presumably buries in the sediments as well but probably only shallowly because its siphons are short.
Revision of a post first published 29 March 2010
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Jessica's Nature Blog 
Fantastic photos of this tiny shell… love your post as well.
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Thank you, Pam. It is not as colourful or as spectacular as some of the seashells you feature in your own site and products …but it is nevertheless a really interesting and unusual one.
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