Two South End banks were robbed Monday morning, and witnesses at both banks gave police a similar description of the culprit. At 10:30 a.m., a man wearing a black or navy hat, white shirt, and black shorts passed a note demanding money to a teller at Brookline Bank on Clarendon Street, Boston police said. The man did not show a weapon and fled toward Back Bay, police said. It was not immediately clear whether the man got away with any money. About 20 minutes later, a man in his mid-30s with clothing matching the description of the man who robbed the Brookline Bank branch entered the Hingham Institute for Savings on Tremont Street, police said.Melissa Hanson can be reached at email@example.com or on Twitter @Melissa__Hanson.