Anomia ephippium vs saddle oyster

Anomia ephippium and saddle oyster both are nouns.

Word	Noun	Adjective	Verb	Adverb
Anomia ephippium	Yes	No	No	No
saddle oyster	Yes	No	No	No

As nouns, Anomia ephippium and saddle oyster are synonyms defined as:

Anomia ephippium and saddle oyster: thin-shelled bivalve having the right valve deeply notched

Anomia ephippium (noun)	saddle oyster (noun)
thin-shelled bivalve having the right valve deeply notched	thin-shelled bivalve having the right valve deeply notched