Description: Thallus filamentous, either up to 16 cms long, dwarf or unicellular. The filaments attached by a basal cell reinforced by rhizoids. Cells cylindrical and somewhat barrel shaped. The dwarf plants form clusters of cells attached to the substrate. The unicellular plants, referred to as the Codiolum-like phase, are unicellular attached by a hyaline stalk.

Habitat: Uncommon. The filamentous form is epilithic on rock and wood in the littoral and sublittoral. The Codiolum-phase grows in the very upper littoral as dark green turfs.

Distribution: Recorded from several areas in the British Isles including Co. Antrim in Ireland, south-east England, the Hebrides and the Faroes. Europe: France, Baltic, Norway, Faroes, Spitzbergen and Iceland. Greenland. Atlantic coast of North America: Canada, Maine, New Hampshire, Massachusetts and Delaware. Pacific North America: from Alaska to California.

Similar Species: Urospora penicilliformis is similar but only slightly constricted at the cross walls. Species of Ulothrix are also similar.

Distribution Map from NBN: Urospora wormskioldii at National Biodiversity Network mapping facility, data for UK.

iNaturalist: Urospora wormskioldii at iNaturalist World Species Observations database.

WoRMS: Urospora wormskioldii at World Register of Marine Species.