#1) There's a tall nest just south of your hideout, with the mask in the nest. Climb the dinosaur bones that go to the top of the hideout, then Paraglide to the nest.
#2) This mask is located on the nose of a very large totem pole on the south end of the map. To get to it, go south from the previous mask and find a large rock that is slanted. Climb a tree nearby to get on top of the rock, then jump and Paraglide to the totem pole, which has blue sparkles, so you can easily stand on it.
#3) Go to the north end of the map and find the river with the big chunks of ice flowing in it. Get on one of these ice chunks and you should see the mask when you go underneath the second wooden bridge.
#4) You need Bob Cooper in order to get this mask. Go back to the same bridge in the previous mask. You'll find an ice wall that Bob can climb on the western side of the bridge. Follow the path of the ice wall to find the mask.
#5) You need Bob Cooper in order to get this mask. There's a giant ice statue of The Grizz on the western side of the map. Go here and then find the small gap in the wooden fence south of it. Drop down and you'll be at the bottom of another ice wall Bob can climb. At the top is this mask.
#6) This mask is found in the Unexpected Ties mission. Play through the mission until you steal the key from The Grizz and go inside the lair. The tiger skin is on the bed, but the mask is behind it.
#7) This mask is found in the Going Up mission. Go through the mission until you encounter falling eggs as you're climbing with Bob. When you reach the top where the first two eggs are falling, don't go left, but instead go right to find the mask.
#8) This mask is found in the Ice Ice Bentley mission. After the section with the painting, you'll come to a tunnel with an egg that rolls down it. Go past this and the next section with the guards and gems until you come to a second tunnel with rolling eggs. At the exit of this tunnel, you'll spot another blocked tunnel opposite of it. Blow it up with a bomb to reveal an alcove with the mask.
#9) This mask is found in the Operation: Jurassic Thievery mission. This one is found when playing as Bob. Here you need to remove some pressure valves to continue. Release the second one, but don'tgo right just yet. Instead, go down past all the flames and then right to find a platform with some small crates hiding the mask.
#10) This mask is found in the Operation: Jurassiv Thievery mission. After the previous part with Bob, you'll be controlling Sly. When you get to the part where you have to use your Paraglider, you should see a platform off to the left just past the two flaming balls. Float to this platform to find the mask.
#11) You need to collect all 12 Treasures in this episode in order to unlock the arcade machine in the hideout. The mask is found in the starting area of the mini-game, but it requires a certain method in order to get it to appear. First, collect all of the time powerups in the starting area, then bounce around bumpers until Bentley makes a remark about it being a pinball machine. The mask will then appear to the left, above the hole with the red outline.
