Note: This family was established by Anagnostidis & Komárek (1988: 397–401) as a segregate of the Oscillatoriaceae, from which it differs chiefly in that the cells are approximately isodiametric or at least not discoid, growing more or less into the original size prior to the next division. In Oscillatoriaceae as circumscribed by Anagnostidis & Komárek (1988: 422–423), division occurs in rapid sequence, resulting in discoid cells. Sheaths may or may not be present in members of either family. The Phormidiaceae comprises three subfamilies: Phormidioideae, including Pelagothrix (treated by those authors as a synonym of Trichodesmium), Phormidium, Porphyrosiphon, Symploca, and Trichodesmium; Microcoleoideae, including Hydrocoleum, Microcoleus, and Sirocoleum; and Spirulinoideae, including Arthrospira and Spirulina.
Note: Bourrelly (1970: 432) merged Arthrospira and Spirulina into Oscillatoria. In contrast, Anagnostidis & Komárek (1988: 421–422), after discussing Bourrelly's treatment and the controversy regarding the distinction between Arthrospira and Spirulina, decided to maintain both genera ad interim.
Spirulina major Kützing, 1843b: 183 (lectotype locality: Weissenfels, Germany fide Drouet, 1968: 17, 20).—Biswas, 1926: 22, pl. VII: fig. 12.— Biswas, 1943: 112.— Desikachary, 1959: 196–197, pl. 36: fig. 13.— T. Pillay, Vijayaraghavan, & Thakurta, 1962: 420.— Basson et al., 1977: 225, 258.— Basson, 1979: 65, pl. IX: fig. 48.— Farghaly, 1980: 135.— N. Anand & Venkatesan, 1985: 102.— G. Subramanian et al., 1989: 310, 311, 314, 316, 319.— S. Silva, 1992a: 114, fig. 27.— Thajuddin & G. Subramanian, 1992a: table III.
Arthrospira major (Kützing) Crow, 1927: 142.
INDIAN OCEAN DISTRIBUTION: India, Kuwait, Madagascar, Mozambique, Saudi Arabia.
Note: The assignment of this species to Arthrospira was supported by C.T. Tseng & Chang (1990: 38), who observed numerous cross walls in sections of trichomes. Drouet (1968: 17, 20) chose a specimen in L as the lectotype of this species and assigned it to Spirulina subsalsa Oersted.