This is kina, the Māori name for the sea urchin or Evechinus chloroticus.
When they're all dressed up with spines and stuff, there's a distinct similarity to a hedgehog (the Middle English name for which was Urcheon).
Not quite as fast, of course, and with a smaller brain (no brain at all, actually - just nerve cells).
And no legs.
A delicacy, so they say, but - despite being an omnivore (necessary for survival as a child, given Mum's cooking skills...), I've never tried one.
You're allowed to harvest 50 a day.
We only saw 7.
Around here, though, Kina means the Kina Peninsula, the Tasman Golf Club and the Kina Cliffs (or Moutere Bluffs), a fairly fragile geological structure of pebbles held together by clay and gradually reverting to its original components.
Helped along - if you believed the papers at the time - by a rich American who bought great chunks of land on the coastline and thought it would be a Good Idea (it wasn't..) to do some landscaping with a bulldozer.
Threats were made to confiscate his toys.
The cliffs were saved.