Sentence:  It was April 22, 1831, and a young man was walking down Whitehall in the direction of Parliament Street. He wore shepherd's plaid trousers and the <WSD>swallow-tail</WSD> coat of the day, with a figured muslin cravat wound about his wide-spread collar. 
Meaning of the word marked with <WSD> tags:  A type of tailcoat with two long tapering tails.(Wp)