the world > animals > invertebrates > subkingdom Metazoa > grade Triploblastica or Coelomata > class Cephalopoda > [adjective] > belonging to order Tetrabranchiata > relating to the nautili > of or relating to conical shell (2)
The straight conical shell typical of early nautiloid cephalopods; a fossil having such a shell.
Of a nautiloid cephalopod: having a straight (or nearly straight) conical chambered shell (orthocone). Also: designating such a shell.