Saint Mark was converted by Peter and accompanied him to Rome, acting as his secretary or interpreter. The Roman people begged Mark to put the accounts of Peter’s frequent talks on our Lord’s life into writing. He did this, under the direction of Peter some time before the year 60. He is represented by a lion because his Gospel begins with St. John the Baptist, “The voice of a lion crying in the desert.” The feast day of St. Mark is April 25.
Source: Lovasik, S.V.D., Rev. Lawrence New Picture Book of Saints. Catholic Book Publishing Company, New York, New York (1979).