Bay seniors on Muni this weekend should not be alarmed when fellow passengers start swinging and swaying in the aisles and pirouetting along the platforms. Stay calm. It is the 8th Annual Trolley Dances this Saturday and Sunday wih six performances from 11 to 2:45 on lines going from Civic Center (it starts at the Library) to West Portal. All for 75 cents with your senior citizens pass. The performers won an award last year from SF Weekly as “Best Transit Ballet”. I did not know there was any competion.