Which of these is not a tributary of cavernous sinus -
Superior petrosal sinus is a draining channel (not a tributary) of the cavernous sinus. 
Tributaries (incoming channels) of the cavernous sinus


Superior ophthalmic vein
A branch of an inferior ophthalmic vein or sometimes vein itself
Central vein of the retina (it may also drain into a superior ophthalmic vein)
Superficial middle cerebral vein
Inferior cerebral vein
Sphenoparietal sinus
Frontal trunk of middle meningeal vein (it may also drain into pterygoid plexus or into sphenoparietal sinus)
Sphenoparietal sinus
Superior petrosal sinus
Superficial middle cerebral vein
Inferior ophthalmic vein