hard clam vs Venus mercenaria

hard clam and Venus mercenaria both are nouns.

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

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

hard clam and Venus mercenaria: an edible American clam; the heavy shells were used as money by some American Indians

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

hard 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