CRINOIDS

Crinoids populary known as sea lilies and feather stars, possess a massive calcite skeleton. They were so abuandant in the Paleozoic seas that their remains formed vast thicknesses of limestone.
Most crinoids are attached to the sea bed by a flexible stem, circular or pentagonal in section, and made up of numerous disclike plates called columnals.
At the top of the stem is a swollen cup or calyx, to which the arms are attached.
The arms are used to filter food from water.

Soon after the animal' s death, the entire skeleton normally falls apart into the small, separate plates called ossicles.
By contrast, well-preserved crinoids are rare and beautiful fossils.