Fuel tank supply pipe query

[Superarnie Mk2]

My car has the fuel tank mounted down in the boot, (not behind the passenger bulkhead like some Mk4's and Superblowers) with the fuel filler mounted in the rear offside wing. A large bore 'L' shaped pipe connects the filler cap into the side of the tank.
   
   Please see images below.
   
   
   
   
   
   You will notice there are two smaller pipes off the main bore pipe. The lower pipe of the two enters the main bore pipe and heads down 3-4 inches before coming to an end. The upper of the two is simply welded onto the main bore pipe. I have noticed there is a similar sized small bore pipe connection on one of the top corners of the fuel tank. I'm guessing the upper one vents to the ground and the lower one connects to the tank??? Can anyone advise??
   
   Hope this makes sense.
   
   Many thanks
   
   Gary

[Mark IV]

One of the bungs should be for the fuel vapor return as the Superblowers had the evaporative emissions system.