Plummeksville, Ark., Jan. 30.- John HL Clayton, brother of Powell Clayton, and one of the most prominent Kepublican leaders in the Southwest, was assassinated Tuesday night at his boarding-house here. Clayton was about to retire when he was shot and killed. Ho ran against C. H. Breckinridge for Congress in the last election and contested the seat. There is greatexcitementover the murder. Clayton lived at Fine Biuft. It is supposed the murder grew out of politics.