Pterostylis erythroconcha, commonly known as the red shell orchid, is a species of orchid endemic to South Australia. As with similar orchids, the flowering plants differ from those which are not flowering. The non-flowering plants have a rosette of leaves but the flowering plants have a single flower with leaves on the flowering spike. This greenhood has a white and green flower with reddish brown markings and a long, fleshy, curved labellum.
Pterostylis erythroconcha is a terrestrial, perennial, deciduous, herb with an underground tuber and when not flowering, a rosette of between three and ten egg-shaped leaves. Each leaf is NaNsigfig=1NaNsigfig=1 long and NaNsigfig=1NaNsigfig=1 wide. Flowering plants have a single flower NaNsigfig=1NaNsigfig=1 long and NaNsigfig=1NaNsigfig=1 wide borne on a flowering stem NaNsigfig=1NaNsigfig=1 high. The flowers are translucent white with reddish-brown stripes and markings. The dorsal sepal and petals are fused, forming a hood or "galea" over the column. The dorsal sepal curves forward with sharp point or a thread-like tip NaNsigfig=1NaNsigfig=1 long. The lateral sepals are held closely against the galea, have an erect, thread-like tip NaNsigfig=2NaNsigfig=2 long and a broad, flat sinus with a small notch between their bases. The labellum is NaNsigfig=1NaNsigfig=1 long, about 4sigfig=1NaNsigfig=1 wide, thick, fleshy and reddish-brown protruding prominently above the sinus. Flowering occurs from April to August.[1] [2]
Pterostylis erythroconcha was first formally described in 1985 by Mark Clements and David Jones from a specimen collected near Corny Point. The description was published in the fourth edition of Flora of South Australia.[3] The specific epithet (erythroconcha) is derived from the Ancient Greek words erythros meaning "red"[4] and konche meaning "snail".
The red shell orchid grows on calcareous sand and limestone, sometimes forming large colonies, usually near the coast, in mallee. It is found in the south-east of South Australia.