Section 11. A mutual bank or stock bank, by vote of at least 2/3 of its voting body, at a meeting duly called for the purpose, preceded by a notice in writing sent to each member of the voting body and to the commissioner by mail at least 60 days before said meeting, may consolidate or merge into or convert into a federally-chartered bank or thrift institution in accordance with the laws of the United States and without the approval of any authority of the commonwealth.