nerita vs neritid gastropod

nerita and neritid gastropod both are nouns.

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

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

nerita: a neritid gastropod having a short smooth or spirally ridged shell with thick usually toothed outer lip and toothed operculum
neritid gastropod: operculate seasnail of coastal waters with a short spiral shell

Other hypernyms of nerita include neritid.

nerita (noun)	neritid gastropod (noun)
a neritid gastropod having a short smooth or spirally ridged shell with thick usually toothed outer lip and toothed operculum	operculate seasnail of coastal waters with a short spiral shell