Bivalve oyster shell

A cluster of devil’s toe nails

Note how these fossil oyster shells are all orientated in the same direction. This could indicate a current was flowing across the sea floor: lob-sided shells such as these tend to be flipped over in the same orientation under such circumstances. However, it is more likely that these are preserved in life position as the oyster sat with its heavy shell anchored in the sediment. That would mean that we are looking at the shells from the underside, and that the sediment has come away to reveal the shells as we see them now.

The popular folklore name for this kind of shell is devil’s toe nail.

Find out more about bivalves on the molluscs pages.

Common name

Bivalve oyster shell

Scientific name

Gryphaea arcuata (Lamarck)


Molluscs > Bivalves


Blue Lias

Time period

Lower Jurassic


c. 200 million years

Where found


Found by



Bridport Museum

Accession number

BRPMG 1212