The Nassariidae, Nassa mud snails (USA), or dog whelks (UK), are a taxonomic family of small to medium-sized sea snails, marine gastropod mollusks in the clade Neogastropoda.
"Dog whelk" also refers to Nucella lapillus.
This family of snails is found worldwide.
These snails are found mostly in shallow water, on sandy or muddy substrates, often intertidally, but sometimes in deep water. They can be present in very large numbers in suitable habitat.