tusk shell vs tooth shell

tusk shell and tooth shell both are nouns.

Word	Noun	Adjective	Verb	Adverb
tusk shell	Yes	No	No	No
tooth shell	Yes	No	No	No

As nouns, tusk shell and tooth shell are synonyms defined as:

tusk shell and tooth shell: any of various seashore mollusks having a tapering tubular shell open at each end and a foot pointed like a spade for burrowing

tusk shell (noun)	tooth shell (noun)
any of various seashore mollusks having a tapering tubular shell open at each end and a foot pointed like a spade for burrowing	any of various seashore mollusks having a tapering tubular shell open at each end and a foot pointed like a spade for burrowing