Patellidae vs mollusk family

Patellidae and mollusk family both are nouns.

Word	Noun	Adjective	Verb	Adverb
Patellidae	Yes	No	No	No
mollusk family	Yes	No	No	No

As nouns, mollusk family is a hypernym of Patellidae; that is, mollusk family is a word with a broader meaning than Patellidae:

Patellidae: a family of marine limpets, containing the sea snails or true limpets (Patellidae)
mollusk family: a family of mollusks

Patellidae (noun)	mollusk family (noun)
a family of marine limpets, containing the sea snails or true limpets (Patellidae)	a family of mollusks