Corallina berteroi Montagne ex Kützing, 1849

Synonym: Corallina caespitosa R.H.Walker, J.Brodie & L.M.Irvine, 2009 
Common name: Tufted Coral Weed.
Description: Base crustose, erect fronds up to 45 mm long, arising from a stiff, unbranched stipe, branching dense, irregularly simple to compound pinnate; intergenicula generally longer than broad, cylindrical at frond base, becoming compressed, wedge-shaped toward the frond apex, typically with 10–15 tiers of medullary cells; apex with 3–4 or more (up to 7) intergenicula or occasionally a single undivided irregular intergeniculum. Spermatangial conceptacles axial, beaked, 500–600 µm in diameter; tetrasporangial conceptacles axial, sometimes pseudolateral, 450–600 µm in diameter; carposporangial conceptacles currently unknown.
Habitat: Intertidal on rock in mid- to lower-shore rockpools; on Mytilus on wave-exposed shores in the west of Ireland. Occasional.
Distribution: Widely distributed in Ireland; in Britain north to Yorkshire; Channel Islands; Northern France (Channel and Atlantic); Portugal; Azores; Italy; Greece; Canary Islands; Ghana; South Africa; California; Mexico, Peru, Chile; Australia (South Australia, New South Wales), New Zealand; Korea, Japan.
Similar species: Corallina officinalis is commoner, is more chalky in colour, has less regular branching, and generally has more rounded articulations. Jania rubens is dichotomously branched; Jania squamata is pinnately branched, but is rare, and tends to be found mostly as epiphytic growths on Ericaria selaginoides in pools.

Photographs © M.D. Guiry