PURPORT

Srila Visvanatha Cakravarti Thakura remarks that when Lord Siva was offering obeisances unto Lord Visnu, Lord Visnu arose and embraced him. Therefore the word srivatsaṅkena is used here. The mark of Srivatsa adorns the chest of Lord Visnu, and therefore when Lord Visnu embraced Lord Siva while being circumambulated, the Srivatsa mark touched Lord Siva's bosom.