From Nookipedia, the Animal Crossing wiki
"I got a Turban Shell! It's like a little fancy hat!"
Donating to the Museum
In New Leaf
Upon donating the Turban Shell to the Museum, it can be found in the large pool in the first room of the ocean exhibit, along with many other species of deep sea creatures. The exhibit has this to say about the Turban Shell:
"They are related to spiral shells. Also, they have lids that cover the openings of their shells. When they walk, they remove the lid and move in the shell by shuffling their feet, much like snails. They become active by night and eat seaweed. They are delicious when cooked in the shell."