It was first described by the French naturalist Charles Alexandre Lesueur in 1817 and is native to the northwestern Atlantic Ocean and the Gulf of Mexico.

[2] P. rapiformis is a small white sea anemone which burrows into the sediment, usually subtidally, but it may be exposed at extreme low water.

[3] When it is disturbed, the tentacles retract and the column inflates to form a globular shape; this is translucent, with longitudinal white stripes, and resembles a small onion.

[4] As a burrowing sea anemone, the pedal disc of P. rapiformis is replaced by a rounded end known as a "physa" which is used for digging.

A dislodged anemone may adopt a globular shape and be rolled about on the sand by the sea until it finds a less turbulent place where it can burrow.