Centroceras clavulatum

Thalli stiff, filamentous, forked with slightly curved tips, forming dense entangled tufts or mats, 1–6 cm high. Branching dichotomously, with lateral proliferations. Branches 100–200 μm diam., with distinct alternation of darkly pigmented nodes and lightly pigmented longer internodes shortening to apices. Nodes spiny (12–14 verticillate spines), spines acuminate, two-three celled, deciduous. The internodes completely corticated by longitudinal rows of rectangular cells of uniform length. Sporangia whorled, tetrahedrally divided, or cruciate, thick-walled, 50–60 μm diam. Cystocarps globose 175x140 μm, sessile, lateral at nodes, partly surrounded by an involucre of curved filaments consisting of several cortical cells. Growing on rocks, epiphytic on macrophytes at middle intertidal to subtidal habitats.

Subtropics and tropics of Atlantic, Indian and Pacific Oceans.