I think you may be right Allira
Shellfish that are alive and close when tapped can be stored up to seven days. This includes oysters and clams. (Mussels should only be stored up to four days).
Shellfish that cannot completely close their shells (razor clams, horse clams, and soft shell clams) can be stored for up to four days. Never store live shellfish in water or in an airtight container (they will die). You can also put the bowl of shellfish into a larger bowl with ice to keep them extra cold. Mussels, steamer clams, or razor clams can be stored up to 3 days