Pelagic organisms, floating on the surface of the open sea, propelling themselves feebly by the pumping movements of the umbrella produced by contraction of the sub-umbral musculature, and capturing their prey with their tentacles.
Certain that there is no int., pelagic larval form.
In the shallower tropical waters, especially on the central ridge, considerable areas are covered by Pteropod ooze, a deposit consisting largely of the shells of pelagic molluscs.
On the pelagic mollusc Phyllirrhoe, attached to it by the subumbral surface, and its tentacles have become rudimentary or absent.
Order Procellariiformes.-Well flying, pelagic, nidicolous.