Apple Pro Keyboard with Linux

I have a 109-key Apple Pro Keyboard. This is my current .Xmodmap file:

! xmodmap $HOME/.Xmodmap

!! Funny Apple Keys:
keycode 174 = F16
keycode 176 = F17
keycode 160 = F18
keycode 204 = F19

!! Why are these different on Apple Keyboard?
keycode 157 = KP_Equal
keycode 182 = Print
keycode 183 = Scroll_Lock
keycode 184 = Pause

!! Remove Caps_Lock
remove Lock = Caps_Lock
keycode 66 = F20