jackknife clam vs razor clam

jackknife clam and razor clam both are nouns.

Word	Noun	Adjective	Verb	Adverb
jackknife clam	Yes	No	No	No
razor clam	Yes	No	No	No

As nouns, jackknife clam and razor clam are synonyms defined as:

jackknife clam and razor clam: marine clam having a long narrow curved thin shell

Other synonyms of jackknife clam include knife-handle.

jackknife clam (noun)	razor clam (noun)
marine clam having a long narrow curved thin shell	marine clam having a long narrow curved thin shell