Soul Eater will replace Samurai 7 once it ends, with a 1:30 a.m. premiere set for February 17. Toonami will run a promo for the series next week.
Soul Eater is based on the manga by Atsushi Ōkubo, which has been running since 2003. The Bones anime adaptation, released on home video by FUNimation, ran for 51 episodes from 2008-2009.
(Thanks to MrDukeDumas for the tip!)