zoology 101
So you are one of the sheep who swallowed Boris's japey anti EU stories live? Snails are molluscs, clams are molluscs, so in a hierarchical categorisation of foods you would put snails, as molluscs, under the category 'shellfish'. In another amazing story, it turns out that large hair animals that defacate in woods are classed as mammals! Crazy European linguistic pedants!