gastropod vs seashell

gastropod

noun
  • Any member of a class of mollusks (Gastropoda) that includes snails and slugs; univalve mollusk. 

seashell

noun
  • The empty shell of a marine mollusk. 

  • A very light pink colour, like that of some seashells. 

adj
  • Of a very light pink colour, like that of some seashell. 

How often have the words gastropod and seashell occurred in a corpus of books? (source: Google Ngram Viewer )