crustacean vs crustaceous

crustacean

noun
  • Any arthropod of the subphylum Crustacea, including lobsters, crabs, shrimp, barnacles and woodlice. 

crustaceous

adj
  • Hard, thin and brittle. 

  • Resembling a crustacean. 

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