Shawne Williams and Darius Washington each chipped in 11 points in the win.
Courtney Beasley matched the game-high 15 points while David Cornwell added 10 for Southern Mississippi (8-17, 2-8), which has dropped eight of its last nine games.
Memphis started the game with a 17-4 spurt, which Chris Douglas-Roberts capped with a layup midway through the first half.
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