The narwhal is a cetacean similar to the beluga that lives in the Arctic Sea. It has a markedly rounded head with a pronounced melon (a mass of adipose tissue at the middle of the forehead); since the narwhal does not have a true dorsal fin, it can swim with ease just below the surface of the ice. It has just one pair of teeth in its jaw, which are upper canines: in the male, the left tooth emerges from the mouth and extends forward in a spiral, projecting a distance equivalent to more than half its body length. Narwhal tusks were traded in Europe by the Vikings as early as the Middle Ages and for a long time enveloped in legend, as people believed them to be the horn of the mythical unicorn. They were attributed magical and miraculous powers, in the belief that they could protect against poisons. Such ideas died out by the end of the 17th century, but these beautiful tusks were still sought after by princes and scientists. Thus it was that Antonio Vallisneri became the proud possessor of a specimen in his collection.
