Cystoidea

Cystoidea or cystoids, is a class of extinct echinoderms in the sub-phyla Blastozoa, that lived attached to the sea floor by stalks. They existed during the Paleozoic Era, in the Middle Ordovician and Silurian Periods, until extinction in the Devonian Period.

Cystoidea

Cystoidea or cystoids, is a class of extinct echinoderms in the sub-phyla Blastozoa, that lived attached to the sea floor by stalks. They existed during the Paleozoic Era, in the Middle Ordovician and Silurian Periods, until extinction in the Devonian Period.