I've always wanted one of these but they are impossible to come by. Narwhal tooth. Ivory. Great thing, usually broken on the tip. Be wonderful to see a full skull and tooth. There may be replicas made.
Once I was in Galisteo, New Mexico with friends and we visited at a house that had a large toothed bird skull on the wall. It was just astounding, nearly three feet long and toothy as heck. It was years before I figured out that it was a dolphin skull. Illegal to have, like lots of things. Eagle, hawk and owl feathers are illegal to possess.
Update: None on Ebay.