Mary Ellen Moylan is a leading ballerina of the famed Ballet Russe de Monte Carlo which opens its annual nation-wide tour at the County Center in White Plains, Monday, Oct. 3, at 8:40 p.m.Ballet Russe Opens Oct. 3As a special event to open their 19th season of presentations in the main auditorium ofthe Westchester County Center in White Plains, the Olneys announce the return of the famed Ballet Russe de Monte Carlo. Coming direct from its annual season at the Metropolitan Opera House, the company will open its nation-wide tour on Monday, October 3, at 8:40 P.M.Representing the best of the time-honored arts associatedwith the ballet, as handed down from generation to generation, the Ballet Russe is recognized by critics and public alike as the most distinguished ballet company appearing before the public today. The extensive repertoire of 28 productions has been augmented this season and new scenery and costumes have been added.Again under the aegis of Sergei J. Denham, the company will feature Frederic Franklin as Maitre de Ballet. Other principals are Alexandra Danilova, Prima Ballerina, and Leon Danielian as Premier Danseur. The company includes the usual bril-