round clam vs Venus mercenaria

round clam and Venus mercenaria both are nouns.

Word	Noun	Adjective	Verb	Adverb
round clam	Yes	No	No	No
Venus mercenaria	Yes	No	No	No

As nouns, round clam and Venus mercenaria are synonyms defined as:

round clam and Venus mercenaria: 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, quahog.

round clam (noun)	Venus mercenaria (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