class Pelecypoda vs class Bivalvia

class Pelecypoda and class Bivalvia both are nouns.

Word	Noun	Adjective	Verb	Adverb
class Pelecypoda	Yes	No	No	No
class Bivalvia	Yes	No	No	No

As nouns, class Pelecypoda and class Bivalvia are synonyms defined as:

Other synonyms of class Pelecypoda include Bivalvia, class Lamellibranchia, Lamellibranchia.

class Pelecypoda (noun)	class Bivalvia (noun)
oysters, clams, scallops, mussels	oysters, clams, scallops, mussels