round clam vs hard-shell clam

round clam and hard-shell clam both are nouns.

Word	Noun	Adjective	Verb	Adverb
round clam	Yes	No	No	No
hard-shell clam	Yes	No	No	No

As nouns, round clam and hard-shell clam are synonyms defined as:

round clam and hard-shell clam: an edible American clam; the heavy shells were used as money by some American Indians

Other synonyms of round clam include hard clam, Mercenaria mercenaria, quahaug, quahog, Venus mercenaria.

As nouns, round clam and hard-shell clam are synonyms defined as:

round clam and hard-shell clam: Atlantic coast round clams with hard shells; large clams usually used for chowders or other clam dishes

Other synonyms of round clam include quahaug, quahog.

round clam (noun)	hard-shell clam (noun)
an edible American clam; the heavy shells were used as money by some American Indians	an edible American clam; the heavy shells were used as money by some American Indians
Atlantic coast round clams with hard shells; large clams usually used for chowders or other clam dishes	Atlantic coast round clams with hard shells; large clams usually used for chowders or other clam dishes