See generally A. Koerte in RE 20.1, cols 540-541, under 'Phormis'; K.J. Dover in OCD(4) 1141, under 'Phormis (or Phormus)'; Kassel-Austin, PCG vol. I pp.174-176. The Suda's version of the name is also found in Athenaeus (see note 6 below) and Themistius (Or. 27.337b), who knows of him from Aristotle (Poetics 1449b6?). An Arcadian named Phormis of Maenalus, who fought as a general in Sicily for Gelon and Hieron (Pausanias 5.27.1,7), was perhaps confused with him (if not the same man).
[1] epsilon 2766.
[2] Tyrant of Gela 491-485 and of Syracuse 485-478.
[3] The [sc. Trojan] Horse and The Sack of Troy appear be alternative names for the same play. The number of his plays is thus six including the Atalanta. See Pickard-Cambridge 289 n.2.
[4] The last three titles refer to the same play. Kepheus was the father of Andromeda, who was rescued by Perseus after he had severed the head of the gorgon Medusa; cf. pi 1786.
[5] The skhnh/ was a tent or booth-like structure (later a stage building) used both as a backdrop to the stage and as a place where an actor could change and make his entrance and exit. See e.g. Plato Laws 817C (web address 1).
[6] Athenaeus, Deipnosophists 14.652A [14.66 Kaibel]; plural there, in fact.