(Storsteinan - The Trondheim fjord / 7.29.2001 / 18 meters)
Athecate hydroids are one of two orders of hydroids. The polyps of Athecate hydroids are NOT protected by a holster, like the polyps of Thecate hydroids are.
Phylum: Cnidaria
Class: Hydrozoa
Order: Anthoathecata
Norwegian: hydroider