helical vs turbinal

helical

adj
  • In the shape of a helix. 

turbinal

adj
  • Having the shape of a cone resting on its apex. 

  • Rolled in a spiral; scroll-like; turbinate; applied to the thin, plicated, bony or cartilaginous plates which support the olfactory and mucous membranes of the nasal chambers. 

noun
  • A turbinate bone. 

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