sea snail vs whelk

sea snail

noun
  • Any saltwater snail; a marine gastropod mollusk with a shell (contrasted with sea slug). 

whelk

noun
  • Certain edible sea snails, especially, any one of numerous species of large marine gastropods belonging to Buccinidae, much used as food in Europe. 

  • A stripe or mark; a ridge; a wale. 

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