glass sponge

glass sponge, any of a class (Hexactinellida, also called Hyalospongiae, or Triaxonia) of sponges characterized by a skeleton that consists of silica spicules (needlelike structures) often united into a delicate geometric network—e.g., that of Venus’s flower basket (q.v.). Glass sponges occur mainly on muddy sea bottoms at great depths.