We found this on a beach in the Bay of Lannion, Brittany, France. What is it? About 6 cm long.
1 Answer
It is the skeleton of Sea Urchin or sea hedgehog.
There are a lot of species (nearly 1000), so it is very difficult to identify just in five minutes, but in general you can start from knowing the Subclass Perischoechinoidea.