Small aquatic herb; corm 3-lobed, 4–6 mm wide. Leaves 5–8, spirally arranged, erect, rigid, tapering abruptly to acute apex, 4–8 (–20) mm long, 1–1.5 mm diam. near mid-point, bright green above, white in basal half; base 2–4 mm wide, winged; peripheral fibre strands, internal hairs and stomata absent; trans-lacunar diaphragms obscure except near base; ligule broadly triangular to reniform, 0.5 mm long; labium present. Sporangia round, 1–1.5 mm diam., translucent; velum absent. Microspores smooth, brown. Megaspores Type I, 0.3–0.5 mm diam.; proximal faces almost smooth; distal face with shallow tubercles and crests, drying greyish white to black.
Grows in shallow rock pools, usually sympatric with Isoetes australis and, sometimes, I. caroli .
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