This lovely specimen is a narwhal, first cousin to Slifkin's dugong. During the middle ages, the beast's long ivory tusk was passed off as one of the most prized objects of all time: unicorn horn. Bishops, who identified the pure white horse with the pure white founder of their Church (I don't get it either) carried staffs made from the tusk, and bits of it were ground into water to serve as cures. Queen Elizabeth I of England had one valued at £10,000, the cost of a small castle.
The New York Times (from where many of the factoids in the preceeding paragraph were gleaned) has an article, today, about this mysterious creature. Seems an enterprising dentist from Connecticut has discovered that the tusk -really a nine-foot whale tooth- is a sensory organ with an extensive nerve system that functions something like an antenna.