POLAR OBSESSION
'(<a href="http://www.j-archive.com/media/2009-12-01_DJ_17a.jpg" target="_blank">Paul Nicklen presents the clue.</a>)  It's easy to see why <a href="http://www.j-archive.com/media/2009-12-01_DJ_17.jpg" target="_blank">these</a> mammals are called unicorns of the sea; <a href="http://www.j-archive.com/media/2009-12-01_DJ_17b.jpg" target="_blank">that</a>'s not a horn, though--it's actually a grooved tooth'
a narwhal