This thing is a type of phytoplankton, specifically a Calcareous phytoplankton. It is classified as a “calcifying organism,” which means that it needs calcium to develop its exoskeleton–its bones are on the outside.
This is probably obvious, but exoskeletons, to me, are cool: Crunchy on the outside with a gooey center. That makes sense to me.
It also made me think of this:
The Spider and the Ghost of the Fly