Special meetings of the council may be called by the clerk on the written request of the mayor or any two (2) members of the council or the city manager on eighteen (18) hours written notice to each member of the council, designating the purpose of such meeting and served personally or left at his usual place of residence by the clerk or someone designated by the clerk. Nothing in this section shall bar a public body meeting in emergency session as defined in Open Meeting Act; Act 267 of 1976, Section 15.265, paragraph (5).