The end of the St. Louis Blues' season also means the overdue end of an era in the National Hockey League.

Center Craig MacTavish, the last player to go without a helmet, announced his retirement today. MacTavish, who completed his 16th season, did not have to wear a helmet because he played before the N.H.L. mandated headgear in 1979-80. He broke in that season with Boston. Players then were allowed to decide for themselves, although they were required to sign a waiver. MacTavish, 38, said he is lucky he was not seriously hurt. ''That's something I'm thankful and grateful for, that I've gotten out of the game with my health.''

Why go without a helmet all those years?

''It was just a comfort thing for me,'' he said.