Oscillaria formosa Bory de Saint-Vincent, 1827a: 474 (type locality: Chaufontaine, Doubs, France fide Drouet, 1968: 166).
Oscillatoria formosa (Bory de Saint-Vincent) Gomont, 1892b: 230.—Biswas, 1926: 21, pl. VI: fig. 10.— Desikachary, 1959: 232, pl. 40: fig. 15.— N. Anand & Venkatesan, 1985: 102.— G. Subramanian et al., 1989: 310, 315, 318–320.— Thajuddin & G. Subramanian, 1992a: table III.
Phormidium formosum (Bory de Saint-Vincent) Anagnostidis & Komárek, 1988: 405.
INDIAN OCEAN DISTRIBUTION: India.
Note: Drouet (1968: 164–165, 166) chose a specimen in PC as the lectotype of this species and assigned it to Porphyrosiphon animalis (C. Agardh) Drouet (1968: 164) (Oscillatoria animalis C. Agardh, 1827: 632; type locality: thermal springs at Carlsbad [Karlovy Vary, Czech Republic]). The latter species, which according to Drouet (1968: 166) usually grows in fresh water and rarely in brackish water, has not been reported from the Indian Ocean.