neritid gastropod vs neritid

neritid gastropod and neritid both are nouns.

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

As nouns, neritid gastropod and neritid are synonyms defined as:

neritid gastropod and neritid: operculate seasnail of coastal waters with a short spiral shell

neritid gastropod (noun)	neritid (noun)
operculate seasnail of coastal waters with a short spiral shell	operculate seasnail of coastal waters with a short spiral shell