neritina vs neritid gastropod

neritina and neritid gastropod both are nouns.

Word	Noun	Adjective	Verb	Adverb
neritina	Yes	No	No	No
neritid gastropod	Yes	No	No	No

As nouns, neritid gastropod is a hypernym of neritina; that is, neritid gastropod is a word with a broader meaning than neritina:

neritina: ornately marked and brightly colored snails of brackish waters
neritid gastropod: operculate seasnail of coastal waters with a short spiral shell

Other hypernyms of neritina include neritid.

neritina (noun)	neritid gastropod (noun)
ornately marked and brightly colored snails of brackish waters	operculate seasnail of coastal waters with a short spiral shell