What was the difference between a Paixhans gun and a Dalgren gun?

The Dahlgren guns were considered an improvement of the Paixhans, which could only fire shells (explosive projectiles) where the Dahlgren could fire shell, solid shot, and canister (lead ball anti-personnel) The Dahlgren guns had a characteristic shape, and SOME were rifled and SOME were larger than the Paixhans guns. Wikipedia has a good brief article on the Dahlgren guns, as well as Paixhans.