Thayer's Greek Lexicon

 1. Syrtis, the name of two places in the African or Libyan Sea
between Carthage and Cyrenaicia, full of shallows and sandbanks,
and therefore destructive to ships; the western Syrtis, between
the islands Cercina and Meninx (or the promontories of Zeitha and
Brachodes), was called Syris minor, the eastern (extending from
the promontories of Cephalae on the west to that of Boreum on the
east) was called Syris major; this latter must be the one referred
to in Acts 27:17, for upon this the ship in which Paul was sailing
might easily be cast after leaving Crete