Echinoids - sea urchins - are among the most commonly found fossils, especially in Mesozoic and Cenozoic sedimentary rocks. In some places their distinctive 5-rayed tests can be found in considerable numbers, weathering into the soil from the limestone and shale bedrocks containing the fossilized remains of these marine animals.
Fossil echinoids have attracted attention since well back into human prehistory, sometimes taking on a religious or magical significance. For example, echinoids, often replaced by flint, are common fossils in the Cretaceous Chalk of England and would have been familiar yet mysterious objects to humans digging for flints to make into tools.
Over the years a great variety of different names and legends have built up around these fossils.