A Pterygodium hallii flower is mostly green, its lip above concave, shiny and spotted dark purple. The lip appendage is shaped like a mitre, a peaked cap with two keels at its base.
The median sepal is elliptic, varying in width, flanked by the lateral petals. The lateral sepals behind are lance-shaped and reflexed, their acute tips pointing down with sac-like depressions higher up. Flower dimensions are 30 mm by 15 mm.
The stigma lobes behind the lip appendage are elliptic. The rostellum is 2 mm tall, its arms 3 mm long. The ovary behind the flower is up to 2,5 cm long (Liltved and Johnson, 2012; Manning, 2007; Le Roux, et al, 2005; iNaturalist).