bivalve vs blue mussel

bivalve

noun
  • Any mollusc belonging to the taxonomic class Bivalvia, characterized by a shell consisting of two hinged sections, such as a scallop, clam, mussel or oyster. 

  • A pericarp in which the seed case opens or splits into two parts or valves. 

blue mussel

noun
  • A medium-sized edible mussel, Mytilus edulis, found on the North Atlantic coast of North America, Europe, and in other temperate and polar waters around the world. 

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