seasnail vs neritid

seasnail and neritid both are nouns.

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

As nouns, neritid is a hyponym of seasnail; that is, neritid is a word with a more specific, narrower meaning than seasnail:

seasnail: any of several creeping marine gastropods with a spirally coiled shell: whelks, tritons, moon shells, neritids
neritid: operculate seasnail of coastal waters with a short spiral shell

Other hyponyms of seasnail include neritid gastropod, whelk, triton, moon shell, moonshell, periwinkle, winkle, limpet.

seasnail (noun)	neritid (noun)
small tadpole-shaped cold-water fishes with pelvic fins forming a sucker; related to lumpfish	operculate seasnail of coastal waters with a short spiral shell
any of several creeping marine gastropods with a spirally coiled shell: whelks, tritons, moon shells, neritids