It does not have a calcareous skeleton but the polyps are connected by a membranous basal connection.

Millepora alcicornis, or sea ginger, is a species of colonial fire coral with a calcareous skeleton.

Embedded in the calcareous skeleton are numerous microscopic polyps.

Acidification affects the corals' ability to create calcareous skeletons, essential to their survival.

Each of these grows into a new colony by secreting a calcareous skeleton and budding.

The calcareous skeletons of this distinctive species have weathered out from the limestone matrix.

A few algae, however, produced hard calcareous skeletons, and were abundant enough to produce small gardens beneath the sea.

Namapoikia rietoogensis is among the earliest known animals to produce a calcareous (probably aragonite) skeleton.

These can be regarded as hard corals which have, through some quirk of evolution, lost the ability to produce calcareous skeletons.

Members of this order have calcareous skeletons, and are strictly marine.