See generally OCD4 s.v. Scylax; FGrH 709.
There is much confusion in the present entry. The travels of Skylax of Karyanda at the behest of king Darius I are mentioned by Herodotos 4.44. He cannot, however, be the author of the Periplous tes thalasses tes oikoumenes (Circumnavigation of the Inhabited Sea) that survives under his name, since from internal evidence it must be fourth-century BC (at least in its present form); accordingly it is known as 'Pseudo-Skylax'. The author of the response to Polybios (pi 1941) must have been later still.
[1] cf. kappa 434.
[2] (For the Pillars see generally eta 464.) In the MS of Suda we read tw=n e)kto\s tw=n as above; editors have suggested e.g. tw=n e)nto\s kai\ e)kto\s tw=n or tw=n e)nto\s tw=n (see Jacoby's apparatus criticus to FGrHist 709 T 1). Emendation would be necessary if this book title referred to the periplous preserved under Skylax's name; but the title Circuit of the Earth may refer to that work.