As Mark states, they are vents and on most carbs they are separate and are angled downwards, however, I have a Fantic 300 in a very original unmolested condition with the Dellorto PHBH 26 BS and it's vent elbows are angled upwards and are linked together by the tube, the owners manual also shows a pic showing them angled upwards and linked. It runs nicely, so I've left it as is. The alloy elbows are only a press fit and can easily be removed or rotated. Also note that this particular carb, PHBH xx BS, doesn't have an air screw as such, it's actually a fuel screw, same function in essence but on a fuel screw in = lean and with an air screw in = rich.
I can't remember which model Dellorto's were which, but if you have an adjustment screw located closest to the motor then it's a fuel screw, if it's closest to the air filter then it's an air screw. Clear as mud really
Hope this helps somehow.
PS: Just looked at your pics again, your Dellorto runs an 'air screw' unlike mine which has a fuel screw. Don't know whether this has any bearing on the type of vent tube setup (linked or open)?