Hard-shell clam and Round clam

Hard-shell clam noun - An edible American clam; the heavy shells were used as money by some American Indians.

Round clam is a synonym for hard-shell clam. In some cases you can use "Round clam" instead a noun phrase "Hard-shell clam".

Round clam noun - Atlantic coast round clams with hard shells; large clams usually used for chowders or other clam dishes.

Hard-shell clam is a synonym for round clam. You can use "Hard-shell clam" instead a noun phrase "Round clam".