That reminded me of a short story-meme:
"Do unicorns have their horn in the middle of their forehead?"
"Yes."
"Do unicorns exist?"
"No."
The horn you saw at the museum is from a
(German: Narwal, a small whale with a long horn,
don't know the English term - so I used
a Dictionary: German<->English
http://www.leo.org/cgi-bin/dict-search.pl?search=Narwal
Search for 'Narwal' produced no results
BUT - they have a lion as icon ... :-)