Conferva paradoxa Dillwyn, 1809 [1802–1809]: 70–71, suppl. pl. F, nom. illeg. (syntype localities: Bangor, Caernarvon, Wales; Brighton, East Sussex, England).
Ulva paradoxa C. Agardh, 1817: XXII.
Enteromorpha flexuosa (Wulfen) J. Agardh subsp. paradoxa (C. Agardh) Bliding, 1963: 79.—Rhyne, 1971: 53.— Egerod, 1974: 132–134, figs. 1–3.— Velasquez & Lewmanomont, 1975: 3.
Taxonomic synonyms:
Scytosiphon erectus Lyngbye, 1819: 65–66, pl. 15C (type locality: Norway).
Enteromorpha erecta (Lyngbye) Carmichael in W. Hooker, 1833: 314.—Bornet, 1885: 17.
Enteromorpha plumosa Kützing, 1843b: 300, pl. 20.I (type locality: Trieste, Italy).—Reinbold, 1907: 554–555.— Kale, 1966: 180–181, pl. 2: figs. 7, 8.— Gopalakrishnan, 1970: 62.— V. Krishnamurthy & H. Joshi, 1970: 3.— H. Joshi & V. Krishnamurthy, 1972: 126, figs. 1B, 2B,Q.— Teo & Wee, 1983: 33, 35, fig. 21.— Untawale, Dhargalkar, & Agadi, 1983: [8].— Phang & Wee, 1991: 56.— S. Balakrishnan, Ravichandran, & Kaliaperumal, 1992: 65.
Enteromorpha hopkirkii M'Calla ex Harvey, 1849: 215 (syntype localities: Torbay, Devon, England; Carrickfergus, Northern Ireland).—Subbaramaiah, Nair, & V. Krishnamurthy, 1977: 74.
Enteromorpha clathrata (Roth) Greville var. hopkirkii (M'Calla ex Harvey) G. Hamel, 1931a: 70.—Børgesen, 1940: 9.
INDIAN OCEAN DISTRIBUTION: Diego Garcia Atoll, India, Indonesia (Sumatra), Madagascar, Mauritius, Singapore, Thailand.
Note: The synonymy was proposed by Bliding (1963: 79–85). Conferva paradoxa Dillwyn, the intended basionym of Enteromorpha flexuosa subsp. paradoxa, is not priorable since it is a later homonym of C. paradoxa Roth (1806: 172–173; syntype localities: Heiligenhafen and "Insula Fimbria'' [Fehmarn], Schleswig-Holstein, Germany) (Spermatochnus paradoxus (Roth) Kützing, 1843b: 335), a species not reported from the Indian Ocean. Ulva paradoxa C. Agardh is treated as a nomen novum in accordance with Art. 58.3. Womersley (1984: 154), basing his opinion on southern Australian populations, recognized Enteromorpha paradoxa (C. Agardh) Kützing (1845: 247) as a distinct species. It is not known with certainty, however, whether these populations are conspecific with the type specimen from Europe.