Gas Cap question

Didn't get a chance to take a better look at it today. I have no idea if my gas tank has a vent on the top of the tank. From what I remember the 4 factory vent tubes were just cut, didn't see them plugged. On a California Emissions optioned car where does the 3rd nipple on the breather on the valve cover come from? Does it connect to the extra canister in trunk near the filler tube?