Hexactinellida

Hexactinellida is a class of sponges, commonly known as glass sponges, whose skeletons are built from four or six pointed siliceous spicules. They are usually classified within the phylum Porifera alongside other sponges, though some researchers consider them distinct enough to warrant their own phylum. Some marine biologists believe glass sponges may be among the longest lived animals on Earth, with tentative age estimates reaching as high as fifteen thousand years for some individuals.