Who is H.S. Teller from Reminiscences of a Stock Operator and what is their importance?

H.S. Teller is a bucket shop operator in St. Louis that treats Livingston poorly and does not allow him even a single trade while he is trying to increase his stake for Wall Street. Teller is very wealthy and runs pool halls as well as bucket shops in several cities. When Teller opens a bucket shop in Hoboken, Livingston figures out a way to manipulate the market and take the shop for a lot of money in return for how he was treated.