ˌ ̷ ̷ ̷ ̷ˈbraŋkēə, -aiŋ- noun plural
Usage: capitalized
Etymology: New Latin, from tetra- + -branchia
: a subclass or order of Cephalopoda including among existing forms only the genus Nautilus, differing from the remaining existing cephalopods in having four gills, four auricles to the heart, and a large chambered external shell, and including many extinct forms — see ammonoidea , nautiloidea ; compare dibranchia