round clam vs quahog

round clam and quahog both are nouns.

Word	Noun	Adjective	Verb	Adverb
round clam	Yes	No	No	No
quahog	Yes	No	No	No

As nouns, round clam and quahog are synonyms defined as:

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

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

As nouns, round clam and quahog are synonyms defined as:

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

Other synonyms of round clam include hard-shell clam, quahaug.

round clam (noun)	quahog (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