Cardtronics (CATM), a large independent operator of automated teller machines, has expanded its network.

The Houston company said Monday it has purchased the assets of Merrimak ATM Group of Rohnert Park, Calif. Financial terms were not disclosed.

Merrimak, which was founded in 1995, provides transaction processing, sales and other services to a nationwide network of 4,800 ATMs that consists nearly entirely of merchant-owned machines. Cardtronics operates nearly 71,000 ATMs worldwide.

The deal is the second for Cardtronics in recent weeks. It bought the assets of ATM servicer Aptus Financial in May.