Stoughton police arrested a man believed to be the bank robber known as the “Brim Beanie Bandit,” authorities said. Daniel Cathcart, 45, of Milton, was arrested late Thursday night in robberies of two banks in Stoughton, said Deputy Police Chief Robert Devine. Cathcart pleaded not guilty at his arraignment Friday in Stoughton District Court to two counts of armed robbery, police said. He is being held on $150,000 cash bail. Cathcart is believed to be connected with a series of Massachusetts robberies over the past two months, but is not currently being charged with the other “Bandit” robberies, Devine said.