Large marine bivalves (5)
I believe the answer is:
clams
(Other definitions for clams that I've seen before include "Their shells are firmly closed" , "Edible bivalve molluscs" , "Proverbially retentive molluscs" , "Marine bivalves" .)
I believe the answer is:
clams
(Other definitions for clams that I've seen before include "Their shells are firmly closed" , "Edible bivalve molluscs" , "Proverbially retentive molluscs" , "Marine bivalves" .)