clade Hypsogastropoda Janthinidae, common name the purple snails or violet snails, are a family of pelagic sea snails, marine gastropod mollusks in the informal group Ptenoglossa of the clade Hypsogastropoda. This planktonic group has modified its foot to produce `rafts` of mucus bubbles used in flotation. ==Genera== Genera in the family Janthin.....