Carpomitra costata (Stackhouse) Batters
Also known as Carpomitra cabrerae Kützing.
Description: Frond narrow, delicate, light brownish-yellow to dark brown, 1-2 mm wide and up to 200 mm long. Branching irregularly dichotomous, midrib more or less obvious (above). Reproductive structures formed on a mitre-shaped apical receptacle.
Habitat: on stones exclusively in the subtidal to 30 m. Terminal tufts of hair 4-6 mm long present in summer. Rare. Many reported records are repeats of single drift findings in the 19th century when the species was a cause célèbre for Victorian collectors.
Distribution: S and W England and Ireland; W Scotland.
Key characteristics: Mitre-shaped receptacles, terminal tufts of hairs, narrow thallus with midrib.
Photograph © Bernard Picton, Ulster Museum.