The Folklore of Gryphaea arcuatas 

Taken from : 

" 'Formed Stones', Folklore and Fossils."  Michael G. Bassett. 

The Devil's Toenail

To both the layman and the professional geologist the fossil oyster Gryphaea arcuata is one of the most easily recognizable species in Britain.  It occurs very commonly in Lower Lias (Jurassic) rocks throughout the country and its evolutionary history has been the subject of spirited controversy among palaeontologists since the 1920s.  Long before that, however, its characteristic incurved shape was familiar to many and it has become widely known as the Devil's toenail.

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On of Robert Plot's 'formed stones' from Oxfordshire was described by him as being 'of the Oyster kind . . . of an oblong figure, very thick, and of a bluish colour'; the specimen is readily identified as a Gryphaea.  Even at the time when these shells had received distinctive names in some parts of the country, for Plot further records that his specimen 'may be the same with the petrified Concha Oblonga crassa, mentioned by Dr. Merret, found in Worcester-shire, and there called Crow-stones, Crow-cups, or Egg-stones'.

In Scotland too Gryphaea has its associations in folklore, being named in Gaelic clach crubain or crouching shell.  According to some 17th and 18th Century reports in Scotland, the possession of a specimen guaranteed a cure for arthritis or other pains in the bones.  As Oakley has observed, this would appear to be a clear case of sympathetic magic, based on the hope that the distorted shape of the shells would in some way help to prevent similar distortion in the owner.

[paragraph omitted]

Taken from : 

" 'Formed Stones', Folklore and Fossils."  Michael G. Bassett.  Department of Geology, National Museum of Wales, Cardiff.  Geological Series No. 1.  Cardiff, October 1982. 

© National Museum of Wales 1982.