The red alga Carradoriella denudata was first reported as Polysiphonia denudata, a species described from England in 1809, and widely reported around in the Atlantic and Indo-Pacific. In 1963, it was reported from Coyote Point, San Francisco Bay, where it is locally common. The genus Polysiphonia has been extensively revised and subdivided, so that the identity of this species is unclear. The native range of Carradoriella denudata is now considered to be confined to the East Atlantic and Mediterranean. The species formerly identified as P. denudata in the northwestern Atlantic is now classified as Kapraunia schneideri. The name Carradoriella denudata is still applied for the San Francisco Bay alga, but could be changed. 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.