Online stock brokerage firm TD Ameritrade touts $38.627 Billion in assets held for their investment clients - now they're the latest to want a piece of the emerging cryptocurrency sector.They're doing this a little differently from other stock brokerage firms which are looking to add cryptocurrency options to their clients using their existing platforms. TD Ameritrade instead has invested in a little-known new exchange called ErisX.said JB Mackenzie, the head of futures and foreign exchange trading at TD Ameritrade.ErisX supports trading, deposits and withdrawals for bitcoin, bitcoin cash, ethereum, and litecoin.added Mackenzie.ErisX is also soon planning to offer Bitcoin futures, pending approval from the CFTC.