The trading losses came on synthetic credit products, which are derivatives tied to credit performance. In disclosing the $2 billion loss on transactions he said were intended to manage risk, Dimon cited "egregious" failures by the bank's chief investment office.
JPMorgan named Matt Zames to lead the office, succeeding Ina Drew, who retired May 14 amid news of the $2 billion loss.
JPMorgan fell 21 cents to $36.03 at 1:50 p.m. in New York. The stock advanced 23 percent this year before the losses were disclosed.
The cases are Baker v. Dimon, 12-cv-03878, and Saratoga Advantage Trust -- Financial Services Portfolio, 12-cv-03879, U.S. District Court, Southern District of New York (Manhattan).