Porifera (sponges), class: Hexactinellida Collection Highlights | Updated 5 years ago Cyliconema cf. apertum Photo by Mark Salotti Named for their siliceous skeletons, glass sponges lack an outer layer, and have spicules (tiny 'needle-like' structures) that support the body’s shape and that form a latticework. They are usually cylindrical, or funnel-shaped. Most species live in deep waters and are common in Antarctic waters. Marine Invertebrates Section View the discussion thread.