Family Spirastrellidae Ridley & Dendy, 1886

Abstract

Spirastrellidae Ridley & Dendy (Demospongiae, Hadromerida) is reduced from its traditional definition by excluding massive sponges, such as Spheciospongia and part of Spirastrella sensu lato, with rare and minute spirasters or amphiasters which are now placed in the Family Clionaidae. The new definition applies to primarily encrusting sponges with prominent layers of relatively large spirasters, amphi- asters or diplasters at the surface and the base or throughout the entire body. In contrast to clionaids, tylostyles in spirastrellids are quan- titatively unimportant and occur in bouquets or simple tracts perpendicular to the substrate, without forming dense networks or tangential layers. Two genera represent the family, Diplastrella and Spirastrella, with several species that are common in shaded tropical and subtropical shallow-water habitats including coral reefs