my 6 petaled sea urchin fossil

this is my hope diamond of things i have found-it has 6 flower petals instead of the normal 5-i was told by a museum currator that it is a one of a kind or freak of nature as he never saw or heard of one and wanted it(i still have it!,lol)i found it on a beach yrs ago -i would like any input or info about it if anyone knows anything-its a little bigger than a old silver dollar and like alot of my things could not be replaced or found agin-anyone know anything about fossils?sea urchins?(not for sale unless you got a mill to spare!,lol)-its millions of years old i am sure of that,its a very nice rare sea urchin-anyone know of any others with the 6 petal design instead of normal 5-please let me know here or email me -jeannieofsc@aol.com(also have a large stamp collection of f/d -signed-covers+silver an gold replicas-about 30+books)