This fossil echinoid came from the chalk cliffs near Ault, France and is preserved with a pristine white calcite. Below is a Echinocorys sp. from the Cretaceous (Turonian) age and was found by my friend Gery.
Adapical surface (top)
Adoral surface (underside or bottom)
For more info on Echinoid anatomy check out the Irregular Echinoid Terminology page at the British Chalk Fossils website.