 A number of species of snails listed here are sometimes also found on lists of marine species.Two listed here, in the genera "Onchidella" and "Otina", are fully marine in habitat, but are pulmonate snails that breathe air at low tide rather than having gills like most marine species.Other species listed here live in habitats that are intermediate between land and saltwater, or in brackish water habitats intermediate between freshwater and full-salinity saltwater.