My favourite typo
In case of an emergency, remain clam.


Like gnu says, mussels tend to accumulate fecal coliform (aka the bad microbes in sewage) and bad toxins (PSP, aka red tide, is one of them - and is at higher levels in the warmer summer months) faster than most clams. Fortunately most mussels you buy in the store are cultured (aquacultured) and tested. Some of the local clams you buy (as they are all mostly dug from the wild) are likely not tested for toxins or fecals, and could be from a questionable source. Some higher scale clam merchants depurate the wild clams before marketing, making them safe (placing them in tanks of high quality water for at least 36 hours to purge contaminants from them).

PSP