tetract vs tetractine

tetract

adj
  • tetractinal; having four rays 

noun
  • An organism having four rays. 

tetractine

adj
  • tetractinal; having four rays 

noun
  • A spicule (of a sponge) that has four branches 

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