The Class Hexactinellida, also known as glass sponges, is a group of deep-sea sponges characterized by their skeletons made of silica spicules, often forming intricate lattice-like structures. They have a unique syncytial tissue (cells fused into a continuous network) and a slow filtration system for feeding on microscopic plankton. Hexactinellids are mostly found in cold, deep ocean environments and play important roles in benthic ecosystems by providing habitat structure for other marine organisms.