ear-shell vs gastropod

ear-shell and gastropod both are nouns.

Word	Noun	Adjective	Verb	Adverb
ear-shell	Yes	No	No	No
gastropod	Yes	No	No	No

As nouns, gastropod is a hypernym of ear-shell; that is, gastropod is a word with a broader meaning than ear-shell:

ear-shell: any of various large edible marine gastropods of the genus Haliotis having an ear-shaped shell with pearly interior
gastropod: a class of mollusks typically having a one-piece coiled shell and flattened muscular foot with a head bearing stalked eyes

Other hypernyms of ear-shell include univalve.

ear-shell (noun)	gastropod (noun)
any of various large edible marine gastropods of the genus Haliotis having an ear-shaped shell with pearly interior	a class of mollusks typically having a one-piece coiled shell and flattened muscular foot with a head bearing stalked eyes