Curious thing with an apparent shell, no idea...

[Lilly Begonia]

Another quite new to me thing turned up on the water bear hunt, it has a seeming hard shell, material inside that and there is no movement. I can't even guess what this is. Anyone else seen one?

[Bruce Taylor]

An ostracod shell, I think (seed shrimp). I could be wrong, though...multicellular critters aren't my thing.