Spirularia

{{Short description|Order of sea anemones}}

{{Automatic taxobox

| image =Cerianthus filiformis.jpg

| image_caption = Cerianthus filiformis

| taxon = Spirularia

| authority = den Hartog, 1977{{cite WoRMS |author=Hoeksema, Bert |year=2015 |title=Spirularia |id=151646 |accessdate=20 June 2017|db=}}

}}

Spirularia is an suborder of marine cnidarians, tube-dwelling anemones, in the class Ceriantharia.{{cite book|author1=Fautin, Daphne G. |author2= Westfall, Jane A.|author3=Cartwright, Paulyn |author4=Daly, Marymegan |author5=Wyttenbach, Charles R.|title=Coelenterate Biology 2003: Trends in Research on Cnidaria and Ctenophora |url=https://books.google.com/books?id=vbySjNMSYuwC&pg=PA261 |year=2007 |publisher=Springer Science & Business Media |isbn=978-1-4020-2762-8 |pages=261–262}} It is one of the two suborders making up Ceriantharia,{{cite WoRMS |title=Ceriantharia |id=1361 |accessdate=27 March 2025|db=}} and includes two families, Botrucnidiferidae and Cerianthidae, and around 99 species. The two suborders differ in the makeup of their cnidome (the types of cnidocyte present), the relative sizes of the oral discs and the shape and structure of the mesenteries.{{cite book|author1=Goffredo, Stefano|author2=Dubinsky, Zvy|title=The Cnidaria, Past, Present and Future: The world of Medusa and her sisters|url=https://books.google.com/books?id=RdYADQAAQBAJ&pg=PA66 |year= 2016 |publisher=Springer International Publishing |isbn=978-3-319-31305-4 |page=66}}

These anemones dwell in parchment-like tubes immersed in soft sediment, and have two whorls of tentacles, the outer tentacles being much longer than the inner ones.