Police said about 240 people arrested for various offenses by 10:30 p.m. That brought the total arrests since convention protests began late last week to at least 551. Nine people were busted yesterday for felony assault on cops trying to arrest a 10th demonstrator for setting afire a papier-maché-and-wood dragon in front of the Garden, cops said. Officers said several protesters hid smoke bombs and ball bearings inside their picket poles. Some of those arrested tossed barriers and threw bottles at cops. One officer was treated for an eye injury and another suffered burns to his hand in the dragon fire.