Foreign exchange revenue at New York-based BNY Mellon, the No. 1 custody bank, surged 31 percent to $165 million from year-ago levels as currency markets underwent more volatility. The bank's total fourth-quarter revenue of $3.69 billion was 2 percent higher than the year-ago period.

BNY Mellon Chief Executive Officer Gerald Hassell, who has been under pressure from shareholders and analysts to rein in costs, also said the bank cut staff expenses by 7 percent compared with the year-earlier period.

BNY Mellon reported adjusted earnings of $667 million, or 58 cents a share, compared with $629 million, or 54 cents a share.

At Boston-based State Street Corp, BNY's largest rival, adjusted net income available to shareholders was $582 million, or $1.37 cents a share. That compared with $514 million, or $1.15 a share, in the fourth quarter of 2013.

State Street said fourth-quarter revenue from foreign exchange trading was $168 million, up 34 percent from the year-ago period. Total operating revenue was $2.72 billion, compared with $2.53 billion in the year-ago period.

BNY Mellon ended 2014 with $28.5 trillion in assets under custody and administration. That was slightly ahead of State Street's total of $28.2 trillion.

(Reporting By Tim McLaughlin; Editing by Chizu Nomiyama)