(photo of Dirk Schories, Germany: specimens from Grevelingen, Netherlands)
This species was known previously as Sagartiogeton undatus. According to recent changes in nomenclature, several thin-walled species of Sagartiogeton, including Sagartiogeton laceratus, Sagartiogeton undatus and Sagartiogeton viduatus are now assigned to the genus Sagartia (while valid generic name for former species of Sagartia is Cylista). For more details see remarks under Cylista elegans.
Taxonomy:
Phylum Cnidaria
Class Anthozoa
Order Actiniaria