Cat’s eye is the common name for the lid or operculum of the common sea snail Turbo smaragdus. When the snail is threatened by a predator or is exposed above the tide, it withdraws into its shell and the operculum seals the opening. After the snail has died and decomposed, the operculum falls free of the shell. The Māori name for cat’s eye is kanohi pūpū, and these tiny ‘lids’ feature in a traditional tale:

Whaitiri was an evil old woman in the South Island who sometimes ate members of her own family. Two of her grandsons, sent to stay the night with her, were afraid she would kill them when they were sleeping. They found some sea snails and took off the cat’s eyes. When they went to bed, they placed the shell lids over their own eyes. This tricked their grandmother into thinking they were wide awake, and she left them alone.