Parvocaulis clavatus

Thallus small, inconspicuous, to 2 mm high, solitary, or in groops, slightly calcified, green. Disc solitary, 1.25-2(-2.5) mm diam., almost flat, composed of radiating 7-11(-13) rays free of each other (fused only at base). Rays (100)-200-350 mm diam., to 1 mm long, cylindrical-clavate, ovoid, with rounded apices. Corona superior consisting of free roundish coronal knobs at base of each ray on the upper surface of disc and bearing 2-3(-4) hairs or hair scars, 50-60 mm diam.; corona inferior lacking. Gametangia are mature rays containing spherical cysts, 85-90(-100) mm diam. Stalk siphonous, 1.2-2.0 mm high, 200(-300) mm diam. increasing in width upwards, rugose, with annular corrugations. Attachment by finger-like rhizoidal holdfast to intertidal rocks, dead coral fragments.

Note: The alga is used in folk medicine.

In tropical waters of Indian and Pacific Oceans. Сommon in countries of the Asia-Pacific Region.