No. 5 Arundel started quickly against the visiting Bulldogs on Friday night and had little trouble the rest of the game, pulling away for a 78-47 victory.
The Wildcats (12-2) sealed the win with consistent foul shooting down the stretch.
Sheronne Vails led the Wildcats with 16 points, and Briana McKellery added 15.
Southern fell to 0-10.
No. 8 Meade 66, Old Mill 44:: Nicole Dixon led the way with 17 points as the Mustangs (15-0) downed the visiting Patriots (9-6). Amani Bailey scored 16 points, and Alissa Chambliss chipped in with 14. The win sets up a showdown with Arundel on Tuesday with both unbeaten in league play.
No. 11 Catonsville 45, Woodlawn 43:: Led by Candace McCray's 10 points and Zoe Whittington's 11 points, the Comets (16-1) earned a tight victory over the Warriors. Entering the fourth quarter trailing by four points, Catonsville took the lead behind the team's strong effort at the free-throw line in the period.
No. 1 Mount St. Joseph 58, Cardinal Gibbons 38:: Ryley Beaumont's 16 points and seven rebounds led the way for the Gaels (23-2), who held the Crusaders (9-11) to just 14 first-half points. Eric Atkins and Matt Miller were also in double figures for Mount St. Joseph, with 12 and 11 points, respectively. Gibbons' Dylan Cormier led all scorers with 18 points, tallying 16 after halftime.
No. 4 Calvert Hall 58, Loyola 42:: Donya Jackson scored 20 points and Jonathan Graham added 17 as the Cardinals (16-4) defeated the host Dons (10-10) in Maryland Interscholastic Athletic Association A Conference play. Mike Fitzpatrick scored 12 for Loyola.
No. 5 Arundel 82, Southern 71, OT:: The Wildcats (14-1) took control of the game in overtime, outscoring the Bulldogs 11-0. Brandon Belt led the Wildcats with 21 points, while Bryan Harris added 21 for the Bulldogs (10-5).