Sponge Bob's Bigger and Older Cousin

Sponge Bob's Bigger and Older CousinSponge BobThe phylum Porifera (sponges; "pore bearing) is divided into three classes, Hexactinellida, Demospongiae, and Calcarea. Calcarea is the oddball of the group, building skeletal elements out of calcium carbonate (like corals and snails) instead of silica. The Hexactinellids (glass sponges) of which I will focus on, are predominately a deep sea group.