People searching for seashells have been left baffled by clusters of "alien" objects that have washed up on beaches in Cornwall. Hundreds of the strange spheres have been spotted by families enjoying strolls along the coastline.
Suggested explanations included dried up baseballs that had fallen overboard from a ship.
But marine experts say they are a type of sea urchin known as the sea potato.
The dead urchins have turned up on beaches in North Devon and at Long Rock between Penzance and Marazion.
They are thought to have been washed in by bad weather.