Citation: M. Clements & D. Jones, sp. Nov1

Synonymy: P. hamiltonii sensu J. Black, Fl. S. Aust. 246 (1943), non Nicholls. , Diplodium erythroconchum

Common name: Red shell orchid.

Description:
Plant moderately robust, 5-13 cm high; non-flowering specimens with basal rosettes 2-5 cm diam., of 3-10 ovate leaves with long petioles (up to 12 mm); at flowering without basal rosette; stem leaves 3-5, lanceolate, 30-50 x 5-8 mm, stem-clasping, all of similar length.

Flower single or rarely 2, erect, maroon or red-brown and translucent white, striated, the white portion generally exceeding the coloured; galea 25-35 mm long, firstly erect, gradually incurved, gibbous near the base, apex broadly obtuse; dorsal sepal shortly acute or with an acuminate tip 2-3 mm long; petals very blunt; lateral sepals (lower lip) erect, conjoined; the lobes separated by a wide truncate sinus, slightly notched and thrust forward about the middle, the tips produced into long filiform points which are at first erect then curve forward and down so as to appear drooping, embracing the galea and exceeding it; labellum on a movable claw, lamina c. 10 mm long, more than 3 mm broad, lanceolate, thick-textured, at first straight, but decurved near the apex, deep-maroon, the tip sometimes slightly 2-fid otherwise subacute, protruding 3-4 mm beyond the sinus, on the upper surface a definite raised median longitudinal ridge; appendage narrow-linear, curved, penicillate; column erect, winged, wings rhomboid, lower lobe quadrate, obtuse with ciliate margins; stigma very prominent, ovate-cordate and high up on the column.

Published illustration: Beek & Foster (1972) Wildflowers of South Australia as P. hamiltonii; Pocock (1972) Ground orchids of Australia, pl. 117 as P. hamiltonii.

Distribution:  Forms small to extensive colonies on limestone or calcareous sands in mallee heathland and chiefly coastal. Locally abundant. S.Aust.: EP, MU, YP, KI, SE. Conservation status: native Flowering time: July — Sept.

SA Distribution Map based on current data relating to specimens held in the State Herbarium of South Australia

Biology: No text

Taxonomic notes: Affinis Pterostylidi scabrae Lindley, a qua floribus rufo- et albo-vittatis; galea cum fauce apertiore labello crasso lato per sinus multo exserto, differt. Holotype: Corny Point, (34º55'S, 137º27'E) 9 August 1956, H. Goldsack 683 (AD). Isolypes: AD, BRI, CBG.

Author: Not yet available