Some Cretaceous echinoids, notably Micraster, Echinocorys and Conulus, have distinctive shapes, leading to the name Shepherd's crowns in English folklore. The five rays converging on the apex of the fossil resemble the ribs of a crown. According to Bassett (1982), shepherds may have come across these fossil echinoids, weathered out of the underlying chalk, while caring for their sheep on the downlands of southern England.
The echinoid test, and/or the sediment infilling it, can be replaced by flint, making it more resistant than the surrounding soft chalk. This facilitates survival of the fossil once exhumed and increases its chances of being collected.