Tridonta borealis
compared to Arctica islandica
Tridonta borealis, width 36mm, Helensburgh. Sub-fossil, aged aproximately 10,000 years. When found, it had an almost complete periostracum, but sadly this flaked off as soon as the shell dried.
This species is not now found living around the coast of Britain
In the first four images, Tridonta borealis is on the right. Arctica islandica is on the left for comparison purposes.
In the picture below, Tridonta borealis is on the left and Arctica islandica is on the right
© Sarah Longrigg
