Analysts polled by First Call expected earnings of 50 cents a share. BellSouth's stock was down 3/8 to 42 1/4. "Our financial performance didn't skip a beat in the third quarter," Duane Ackerman, BellSouth's chairman and chief executive, said in a statement. Revenues for the Atlanta-based company increased 9.5% to $6.4 billion from $5.8 billion in the 1998 third quarter.