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The name Echinoid comes from the Greek echinos which translates as hedgehog. They are commonly known as sea urchins and are related to star fish.
Echinoids have been around for a long time, about 480 million years. There are still echinoids alive today, although these ones are ancient.
There is a long English folk tradition calling these Fairy Loaves and Pixie Helmets. In Denmark they are known as thunderstones as they are thought to ward off lightning. These come from Madgascar and all have the five fold symmetry.