Fucus debilis Forsskål, 1775: 191 (type locality: Mokha, Yemen).
Gracilaria debilis (Forsskål) Børgesen, 1932c: 7.—Thivy, 1952: 174.— Chacko, Mahadevan, & R. Ganesan, 1955: 12.— S. Dixit, 1966: 16.— Desikachary, 1967: 24, pl. III: fig. 3.— V. Krishnamurthy & H. Joshi, 1970: 21.— Chauhan & Mairh, 1978: 35.— Untawale, Dhargalkar, & Agadi, 1983: [32].— Barratt et al., 1984: species list.— V. Krishnamurthy & Rajendran, 1986a: 95, fig. 9.— V. Krishnamurthy & Rajendran, 1987a: 10, 14, fig. 8, table 1.— V. Krishnamurthy, 1989: figs. 2C, 6A.— V. Krishnamurthy, 1991: table V.
Polycavernosa debilis (Forsskål) Fredericq & J. Norris, 1985: 152.—Ormond & Banaimoon, 1994: 118.
Taxonomic synonyms:
* Gigartina obtusa Greville ex J. Agardh, 1852 [1851–1863]: 590 (type locality: "Ad oras Indiae orientalis'' [India]).—Newton, 1953: pl. III: figs. 1, 6.
Gracilaria obtusa (Greville ex J. Agardh) Harvey, 1857a: no. 30 bis.—G. Murray, 1887: 27.— De Toni, 1900: 443.— De Toni, 1924: 272.— V. Krishnamurthy & H. Joshi, 1970: 21.— Umamaheswara Rao, 1974b: 687–688, figs. 4g–j, pl. III:A,C.— Untawale, Dhargalkar, & Agadi, 1983: [32].— Chennubhotla, Kaliaperumal, & Kalimuthu, 1987a: 106–107.— Kaliaperumal, Kalimuthu, & Ramalingam, 1990: table 1.
* Gymnogongrus javanicus Sonder, 1854: 2, 3–4 (syntype localities: Indonesia: southeast Java and Bima Bay, Sumbawa).—De Toni, 1897: 250.— De Wildeman, 1899: 62.— Zaneveld, 1959: 122.
* Sphaerococcus obtusus Kützing, 1869: 8, pl. 21: figs. a–d (type locality: Sri Lanka).—Newton, 1953: pl. III: fig. 2.
Ceramianthemum obtusum (Kützing) Kuntze, 1891: 887.
* Gracilaria fergusonii J. Agardh, 1901: 60–61 (`fergusoni') (type locality: Sri Lanka).—De Toni, 1924: 256.— Børgesen, 1938b: 222–224, figs. 5, 6.— I. Joseph et al., 1948: 54, table XVI.— Newton, 1953: pl. III: fig. 3.— Durairatnam, 1961a: 60.— S. Dixit, 1966: 16.— Desikachary, 1967: 24, pl. III: fig. 4.— Umamaheswara Rao, 1969d: 45.— V. Krishnamurthy & H. Joshi, 1970: 21.— K. Srinivasan, 1973: 14, pl. XIV.— Jaasund, 1976: 87, fig. 174.— Jaasund, 1977c: 420.— Rama Rao, 1977c: 95, table 2.— P. Subba Rao, Rama Rao, & Subbaramaiah, 1977: 82, 84–85, table 1.— Knutzen & Jaasund, 1979: 3.— V. Krishnamurthy, 1980: 54.— Lawson, 1980: 48.— Dantanarayana et al., 1981: 11.— Mshigeni, 1982: 146.— Untawale, Dhargalkar, & Agadi, 1983: [32].— Mshigeni, 1984: table 1.— Balasundaram, 1985: 180 ff.— Kalugina-Gutnik, 1985: 96, 97, fig. 2.— Mageswaran, V. Balakrishnan, & Balasubramaniam, 1985: tables 1–5.— Payri, 1985: 640.— Subbaramaiah, 1985: 140.— Nair et al., 1986: 737.— V. Krishnamurthy & Rajendran, 1987a: 11, 14, fig. 11, table 1.— Bandara et al., 1988: 215.— V. Krishnamurthy, 1989: fig. 2D.— V. Krishnamurthy & Balasundaram, 1990: 7, fig. 5, table I.— V. Krishnamurthy et al., 1990: figs. 3, 6.— V. Krishnamurthy, 1991: table V.— Nair et al., 1993: 185, 193.— Oyieke & Kokwaro, 1995: 45.
Misapplied name (fide Newton, 1953: 412):
Gracilaria wrightii.—Grunow, 1867: 83.— J. Agardh, 1876: 422.— Bornet, 1885: 19.— De Toni, 1900: 446.— J. Agardh, 1901: 78.— Hariot, 1902: 472.— De Toni, 1924: 261.— Weber-van Bosse, 1928: 438.— J. Price, 1971: 135, 149, 167, 168, 170, figs. 22a,b.
INDIAN OCEAN DISTRIBUTION: Aldabra Islands, India, Indonesia (Java), Kenya, Madagascar, Nicobar Islands, Oman, Réunion, Sri Lanka, Tanzania, Yemen.
Note: The synonymy, with the exception of Gymnogongrus javanicus, was proposed by Newton (1953: 410–413). The basionym of Gracilaria wrightii (Turner) J. Agardh (1852 [1851–1863]: 599) is Fucus wrightii Turner (1809–1811: 31–32, pl. 148), for which Turner cited collections from the West Indies and the Red Sea. Noting that two different species were involved, Newton retained the name for the West Indian species inasmuch as Wright had supplied Turner with a collection from Jamaica. Although she stated that Red Sea and Indian Ocean records of Gracilaria wrightii pertain to G. debilis, she listed these misapplications in the formal synonymy of G. canaliculata Sonder. Weber-van Bosse (1928: 438), after examining an apparently authentic specimen of Gymnogongrus javanicus and an example of no. 65 of Ferguson's Ceylon Algae, on which Gracilaria fergusonii is based and which had been determined by Grunow as Gracilaria wrightii var. ceylanica, concluded that both specimens were conspecific with material that she had determined as G. wrightii.