Phrontis tiarulaPhrontis tiarula, common name the western mud nassa, is a species of small sea snail with gills and an operculum, a marine gastropod mollusc in the family Nassariidae, the nassa mud snails or dog whelks.DescriptionThe length of the shell varies between 9 mm and 20 mm.DistributionThis species occurs in the Pacific Ocean from California to Mexico.Feeding habitsThese snails are exclusively scavengers.