Listings that appeared Oct. 3 and Oct. 5 about the discovery of the Antikythera Mechanism were incorrectly headlined "Roman Computer."  The mechanism to be discussed 6:30 p.m. Oct. 7, at Discovery Museum and Planetarium, 4450 Park Ave., Bridgeport, is Greek. It was discovered in 1901 among the remains of an ancient Roman shipwreck.