Beavers have 6 of these on their heads (in 2 sets of 3); 1 is transparent & helps in swimming underwater
They 
can remain underwater for 15 minutes without surfacing, and have a set of 
transparent... [DOC] [TLE] Beaver (6) - Photography by Natalie [PAR] Felling and gnawing trees with their strong teeth and powerful jaws, they create 
massive ...