Seven Arkansans are listed among the 400 richest Americans by Forbes magazine. Not surprisingly, four of them are relatives of late Wal-Mart founder Sam Walton. The Waltons listed by the magazine share the Number Four ranking with an estimated 20 and a half billion dollars each. They are 55-year-old Jim Walton, 57-year-old John Walton, 59-year-old S- Robson Walton and 84-year-old Helen Walton. Listed at number 140 is Little Rock investment banker Jackson Thomas Stephens, age 80, with one-and-a-half billion dollars. Lieutenant Governor Winthrop Rockefeller came in at number 195 with one-point-two (b) billion dollars. The last Arkansan listed is Donald John Tyson of Springdale-based Tyson Foods. Forbes estimated the 73-year-old`s worth at 630 million dollars. ----- Microsoft Corporation founder Bill Gates remains in the top spot on the list. He has an estimated 46 billion dollars. Forbes says the net worth of America`s richest people is 955 billion dollars.