Plocamium rigidum Bory de Saint-Vincent, 1834: 164 (type locality: Cape of Good Hope, South Africa).—J. Agardh, 1851 [1851–1863]: 397.— J. Agardh, 1876: 340–341.— Barton, 1896: 197.— De Toni, 1900: 592.— Reinbold, 1907: 572.— Mazza, 1908 [1905–1918]: 11–13.— Kylin, 1938: 12, pl. 3: fig. 8.— Stephenson, Stephenson, & Bright, 1938: 5.— Stephenson, 1939: 534.— Stephenson, 1944: 351.— Stephenson, 1947: 307.— Simons, 1964a: 187, 189, figs. 4a–c.— Simons, 1969: 259, fig. (s.n.).— Simons, 1977: 51, fig. 149.— Joubert & Hanekom, 1980: appendices 1, 3.— Bolton, 1986: 253.— Seagrief, 1988: 56, fig. 5:10.— R. Anderson & Stegenga, 1989: 304, 305, 306.— Bolton & Stegenga, 1990: 237.— Branch et al., 1994: 334, pl. 159.8.
Taxonomic synonym:
* Plocamium condensatum Kützing, 1866: 17–18, pl. 49: figs. c, d (type locality: Cape Agulhas, Cape Province, South Africa).—Delf & Michell, 1921: 110.
Misapplied name (fide Papenfuss notes):
Plocamium membranaceum.—Stephenson, Stephenson, & du Toit, 1937: 355, 373.
INDIAN OCEAN DISTRIBUTION: Amsterdam Island, South Africa.
Note: The synonymy was proposed by J. Agardh (1876: 340–341).