Description: Filaments fine, uniseriate, unbranched, in tufts no more than 8 cms long. Cells irregular in length. Rhizoids growing down reinforcing attachment.

Habitat: Generally common. Epilithic in the upper littoral and sometimes lower down.

Distribution: Widespread in the British Isles. Europe: Portugal, Spain, France, Netherlands, Germany, the Baltic, Norway, Faroes, Spitzbergen and Iceland. Atlantic coast of North America: Canada, Maine, New Hampshire, Massachusetts, Rhode Island, Connecticut, New Jersey, Delaware and Virginia. Further afield: Arctic Seas from the Kara Sea to the west coast of Greenland in Baffin Bay, Pacific coast of North America from the Bearing Sea to California and Japan.

Similar Species: Other species of Urospora and Ulothrix, however the cells of Urospora penicilliformis are only slightly constricted between the cells and Ulothrix has a plate-like or stellate chloroplast, not a perforated plate.

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

iNaturalist: Urospora penicilliformis at iNaturalist World Species Observations database.

WoRMS: Urospora penicilliformis at World Register of Marine Species. Accepted name: Urospora penicilliformis (Roth) Areschoug, 1866. AphiaID: 144420.

Classification: Biota; Plantae; Viridiplantae; Chlorophyta; Chlorophytina; Ulvophyceae; Ulotrichales; Ulotrichaceae; Urospora