Sextus Decretalium
Black's Law Dictionary · Henry Campbell Black, M.A. · 1910
Black's Law Dictionary
Lat. The sixth (book) of the decretals; the sext, or sixth decretal. So called because appended, in the bsdy of the canon law, to the five books of the decretals of Gregory IX.; it consists of a collection of supplementary decretals, and was published A. D. 1298.
Buth Hor. Jur. 172; 1 Bl. Comm. 82.