Modern walruses do not use their teeth to chew molluscs like sea otters do. Instead, they hold a clam in their lips, and the vaulted palate allows them to use their tongue as a powerful piston to suck the soft parts right out of the clam shell. The shell is then dropped to the seafloor, never entering the oral cavity.
From the Wikipedia entry for “Imagotaria downsi” an extinct species of  walrus.
Wow! That is a cool fact! Thank you, World Wide Walrus Web!