Lewis Short
(adjective) : quintus-dĕcĭmus, a, um
* The fifteenth (class.): locus,Cic. Inv. 1, 54, 105: quintisdecimis castris,Liv. 45, 33 fin.: in libro quintodecimo,Gell. 1, 16, 11; often separately: quinto decimo Kal. Dec.,Col. 11, 2, 88; and sometimes in reverse order: anno decimo quinto,Eutr. 1, 19.
Charlton T. Lewis, Charles Short, A Latin Dictionary