Amphiroa anceps

Thallus heavily calcified, in dense clumps, articulated, rigid, purple to grayishpink in color, 2–10(–15) cm high. Branching in one plane, dichotomous with very narrow angles in the upper part. Lower segments terete, compressed to flat above, nearly all of the same length, 6–10(–15) mm long, (0.5–)1–3(–4) mm broad. Joints сonspicuous, non-calcified. In longitudinal section, segment consist of numerous curved tiers of medullary cells, 2–5 layers of longer cells (40–70 μm long) alternating with one layer of short cells, 10–25 μm long. Cortex composed of compact filaments of 3–8 isodiametric or slightly elongate cells, 7–12 μm diam., with terminal epithelial cells. Conceptacles prominent, to 500 μm diam., with central pore, mostly on the surface of one side of the segments. Conceptacles with a central tuft of elongate cells and tetrasporangia. Tetrasporangia elongate-ovoid, 20–50 μm diam., zonately divided. Attachment by crustose holdfast, 2–10 mm across. Growing on hard substrates in the intertidal and upper subtidal zones.

Tropical and subtropical waters.