Pterostylis erythroconcha

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 60–150 mm (2–6 in) long and 3–8 mm (0.1–0.3 in) wide. Flowering plants have a single flower 25–30 mm (1–1 in) long and 9–11 mm (0.4–0.4 in) wide borne on a flowering stem 60–150 mm (2–6 in) 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 1–2 mm (0.04–0.08 in) long. The lateral sepals are held closely against the galea, have an erect, thread-like tip 25–30 mm (0.98–1.2 in) long and a broad, flat sinus with a small notch between their bases. The labellum is 16–20 mm (0.6–0.8 in) long, about 4 mm (0.2 in) wide, thick, fleshy and reddish-brown protruding prominently above the sinus. Flowering occurs from April to August.[2][3]

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.[1] The specific epithet (erythroconcha) is derived from the Ancient Greek words erythros meaning "red"[4]^:308 and konche meaning "snail".[4]^:530

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.[2][3]