Vermetid worm (Dendropoma maxima) colony. Vermetid worms, or worm snails, are a species of seal snail gastropod. Vermetid gastropods are unusual snails in that they secrete the calcareous tube in which they live. These ones have operculums (lids) covering the open ends of their tubes. They feed by trapping particles in a mucous net. Photographed in Indonesia.