Lewis Short
Serrhēum | -rhīum | -rīum (noun N) : (, )
* A promontory in Thrace, with a fortification: alia castella, Cypsela et Doriscon et Serrheum,Liv. 31, 16, 5; Mel. 2, 2, 8.— Form Serrium,Plin. 4, 11, 18, § 43.
Charlton T. Lewis, Charles Short, A Latin Dictionary