When I'm walking on the beach, I can't help but notice the shining jingle shells. So, when I see one that I think is a pretty color or different, I pick it up and put it in my pocket. There's hardly a time that I go home from the beach without jingles.
The thin, translucent clamshell halves make a jingling sound when they are shaken together. Their surface is shiny like frosted nail polish. These bivalves (two-part shells) attach themselves to hard objects in the water and often other shells, by means of threads that extend from a hole in the lower valve. Their shape is often influenced by the shape of the object they're attached to. The upper valve is concave, and the lower valve is flatter. They vary in size, up to a couple of inches wide; most that I see are no more than an inch wide.
Sometimes they are used to make jewelry, wind chimes, strung together to make wind chime curtains, or many other craft items. Just recently, I saw them thrown at a beach wedding instead of rice. The colors vary from shades of white, yellow, and black.
Other names for the Jingle Shells are 'Mermaid's Toenails', and 'Saddle Oyster'.