what is a piece of the limestoneresidence of an animal from the Cnardaria?

Answer 1

The Cnidaria are a phylum of invertebrates that include the jellyfish, hydra, anemones, and corals. Corals have a free-swimming immature larval form, but then the individual coral animals settle on a substrate and produce a calcium carbonate (limestone) "housing" (residence) surrounding their bodies. They often settle on the "skeletons" of coral animals that have already died. Corals tend to form reefs (both by sexual reproduction and by budding which can become quite large.

Answer 2

That would be coral.