Padina pavonia (Linnaeus) J.V. Lamouroux
Description: Thallus fan-shaped, becoming funneled when older, to 120 mm long and 10-100 mm broad; fronds thin and translucent, olive to yellow-brown, darker near the base, irregularly forked-lacinate, lacking a midrib; with silvery concentric bands of calcium carbonate deposition (above); attached by a persistent tangled mass of attachment rhizoids. Apices ringed with brownish or silvery hairs.
Habitat: lower intertidal in pools and on rock in summer; generally associated with soft rock, sand and detritus.
Distribution: S coast of England, southwards to the Mediterranean. Irish report from Cork seems to be of depauperate populations that have not persisted.
Key characteristics: Absence of midrib, fan- and funnel-shaped, silvery concentric bands.