Citigroup to shutter LavaFlow stock trading venue

``Critics say the alternative stock trading venues add to the fragmentation of the market, increasing complexity and costs for market participants... LavaFlow was the sixth largest ATS for stocks for the week of Nov. 10, according to the latest data from the Financial Industry Regulatory Authority (FINRA.) The trading venue is known as an electronic communications network (ECN) that unlike like other ATSs known as "dark pools" displays some information about pending orders in the system.''