Hexactinellid sponges are sponges with a skeleton made of four- and/or six-pointed silaceous spicules, often referred to as glass sponges. Overview They are usually classified in the Class Hexactinellida along with other sponges in the phylum Porifera, but some researchers consider them sufficiently distinct to deserve their own phylum, Symplasma. Hexactinellids are relatively uncommon and are mostly found at substantial depths, although the species Oopsacas minuta has been found in shallow w… (More on Hexactinellid)