Kapraunia schneideri is a red algae from the northwestern Atlantic whose history has undergone several taxonomic revisions based on morphological and molecular genetic studies. We tentatively interpret former reports of Polysiphonia denudata from San Francisco Bay (Josselyn and West, 1985), which was first found in the brackish Lake Merritt, in Oakland in 1963 (J. T. Carlton), as the Northwest Atlantic estuarine species Kapraunia schneideri. K. schneideri was earlier identified on the U.S. Atlantic coast as the European P. denudata; but was found to be different than European type species. It was reclassified as Polysiphonia schneideri in 2010 and then later to Kapraunia schneideri as part of a new genus. We note that morphological and genetic confirmation of San Francisco Bay populations as K. schneideri is required. This seaweed grows on shells and stones on soft-sediment habitat and grows from 50–500 mm, with feathery, widely spaced branches. Herbarium specimens are dark red to maroon.