Conferva diaphana Lightfoot, 1777: 996 (type locality: Scotland).
Ceramium diaphanum (Lightfoot) Roth, 1806: 154–155.—Dickie, 1874b: 197.— Sonder, 1879: 84.— Sonder, 1880: 12.— Pocock, 1958: 27.— Simons, 1977: 61, fig. 186 (C. diaphanum-group).— Lawson, 1980: 37.— Seagrief, 1980: 27, fig. on pl. 10.— Lambert & Steinke, 1986a: 54.— Seagrief, 1988: 62, fig. 5:13.
Taxonomic synonyms:
Ceramium diaphanum (Lightfoot) Roth var. tenuissimum Roth, 1806: 156 (type locality: not specified).
Ceramium tenuissimum (Roth) Areschoug, 1847b: 322, nom. illeg.—Hauck, 1888 [1886–1889]: 87.— Farghaly, 1980: 164.— Lawson, 1980: 37.— Jagtap, 1987: table 1.— Ormond & Banaimoon, 1994: 119.
Hormoceras nodosum Kützing, 1842: 732 (syntype localities: Golfo di Genova and Trieste, Italy).
Ceramium nodosum (Kützing) Griffiths & Harvey in Harvey, 1847 [1846–1851]: pl. XC.—Askenasy, 1888: 39 (with query).
Gongroceras nodiferum Kützing, 1849: 678 (lectotype locality: Lessina [Hvar], Croatia fide Kützing, 1862: 24).—G. Martens, 1868: 28, 82–83.— De Wildeman, 1897a: 178.
INDIAN OCEAN DISTRIBUTION: Australia, Indonesia (Sumatra), Laccadive Islands, Madagascar, Mauritius, Mozambique, Somalia, South Africa, Tanzania (Zanzibar), Yemen.
Note: J. Agardh (1851 [1851–1863]: 120–121) placed Hormoceras nodosum and Gongroceras nodiferum in the synonymy of Ceramium tenuissimum, which he erroneously attributed to (Lyngbye) J. Agardh. Ceramium tenuissimum, in turn, was referred to C. diaphanum by Maggs & Hommersand (1993: 54–55). Ceramium tenuissimum (Roth) Areschoug is a later homonym of C. tenuissimum Bonnemaison (1828: 132; syntype localities: France: Saint-Pol-de-Leon and Brest, Finistère; Saint-Malo, Ille-et-Vilaine), which was transferred to Aglaothamnion by Feldmann-Mazoyer (1941: 469, errata 3). According to L'Hardy-Halos & Rueness (1990: 363), however, the placement of C. tenuissimum Bonnemaison within Aglaothamnion is uncertain because details of the carposporophyte, which are essential in differentiating species, are unavailable, the type being a tetrasporophyte.