I recently purchased a marble mouse but soon found out that the mouse buttons do not function as expected on Ubuntu. This was soon remedied with the following tweaks to the Edit the locate xorg.conf.d directory using command
locate xorg.conf.d | grep d$
edit the 50-marblemouse.conf in the xorg.conf.d, replace the inputClass with the section below
### START FILE SNIPPET ###
Section "InputClass" Identifier "Marble Mouse" MatchProduct "Logitech USB Trackball" MatchIsPointer "on" MatchDevicePath "/dev/input/event*" Driver "evdev" Option "ButtonMapping" "1 8 3 4 5 6 7 2 9" Option "EmulateWheel" "true" Option "EmulateWheelButton" "9" Option "ZAxisMapping" "4 5" Option "XAxisMapping" "6 7" Option "Emulate3Buttons" "false" EndSection
### END FILE SNIPPET ###
Button numbers
1 – Large left button
8- Small left button
3 – Large right button
9 – Small left button