Snakes' and other eggs
Fossil echinoids have also been equated in folklore with the eggs of snakes. Called Ovum anguinum by Pliny (Kennedy 1976), druids thought that magical snake eggs were formed by froth from snakes congregating at midsummer. The froth, shaped into a ball, could be stolen from the snakes during midsummer's eve but would only retain its magical powers if the ball was kept on a piece of cloth (Kennedy 1976).
The thief was required to run away with the snake egg from the angry snakes, preferably over a river across which the snakes could not swim. The 'egg' had indentations on it, supposedly the points where the snakes were once attached. The egg was said to protect its owner from poisons and deadly vapours (Kennedy 1976) as well as from defeat in battle (Oakley 1974).
In other places it was thought that these fossil echinoids were actually tortoise eggs that have hardened into stone (Brookes 1763). Brookes (1763; p. 307) notes that they were commonly found in Malta where “...they are called by the country people the Breasts of St. Paul, because sometimes two of them are found together.”
The fossil echinoids that come from the Chalk of Kent have been referred to as Chalk eggs. John Woodward (1729) suggested that the chalk filling the tests was a good cure for an acidic stomach. Given the composition of this chalk, which is calcium carbonate, this is not an unreasonable idea. Woodward also suggested that chalk eggs are good for sea-sickness, some sea-farers not venturing on board ship without them.