Rhynchospora megapotamica (A.Spreng.) Pfeiffer (1943: 129) .

Type:—Ad fluv. magn. (Rio grande) Brasil. Sello (B †, F neg. 12153, left-hand specimen) (Fig. 41). Lectotype, designated by Moraes & Sennikov (2021: 2):— BRAZIL. Rio Grande, Herbier Impérial du BRÉSIL N.o 134 = Sellow s.n. (P 00267466!). BRAZIL. Rio Grande do Sul: Pântano Grande, 30º13’44.75”S, 52º21’46.08”W, 20 December 2011, Silva Filho 1463 (superseded neotype ICN 00029395!, designated by Silva Filho et al. 2017: 182, isoneotype NY n.v.).

Basionym: Scirpus megapotamicus Sprengel (1828: 4) .

Homotypic synonyms: Isolepis megapotamica (A.Spreng.) Dietrich (1832: 132) .

Cyperus megapotamicus (A.Spreng.) Kunth (1837: 10) .

Pycreus megapotamicus (A.Spreng.) Nees von Esenbeck (1842: 6) .

Chlorocyperus megapotamicus (A.Spreng.) Rikli (1895: 27) .

Heterotypic synonyms: Rhynchospora kunthii var. composita Nees von Esenbeck (1842: 147) ≡ Hygrocharis luzulaeformis Nees von Esenbeck (1842: 143 [sub Rhynchospora minor Nees], 147 [in nota]. 1842 ≡ Rhynchospora luzuliformis Boeckeler (1873: 632) .

Type:— BRAZIL. Sellow in Herb. Reg. Berol. ”, Sellow s.n. (B †). BRAZIL. Rio Grande do Sul: Pedro Osório, BR 116 km 565, 31º55’47.9”S, 52º44’05.3”W, 31 Oct 2006, Trevisan 686 (neotype ICN00014956, designated by Silva Filho et al. 2017: 182) .

Rhynchospora maculata Maury (1889: 146, t. XLIII A).

Type:— PARAGUAY. Plaine de Piraju-bi, dans les praires humides”, 1 Sep 1874, Balansa 457 (lectotype P00267468!, designated by Moraes & Sennikov 2021: 3, isolectotype K000632426!). Syntypes: BRAZIL. Rio Grande, Herbier Impérial du BRÉSIL N . o 134 = Sellow s.n. (P00267466!) (Fig. 41); URUGUAY. Banda Oriental, St.- Hilaire Catal. C 2 No 2057 (P00267471!); idem, St.- Hilaire Catal. C 2 No 2144 (P00267470!); URUGUAY. Montevideo, Ile S . Gabriel, 3 Nov 1855, Courbon s.n. (P00267467!) .

Rhynchospora luzuliformis var. elongata Kuntze (1898: 336) .

Type:— PARAGUAY. Rio Tebicuari, Sep 1892, Kuntze 88 (lectotype NY00051554!, designated by Moraes & Sennikov 2021: 3; probable isolectotype US02255080! [Kuntze 87]) .

Rhynchospora luzuliformis var. subcapitata Kuntze (1898: 336) .

Type:— PARAGUAY. Villa Florida: 2 Oct 1892, Kuntze 86 (lectotype NY 00051556!, designated by Moraes & Sennikov 2021: 3). Syntype: URUGUAY. Sierra de Solis: Nov 1892, Kuntze s.n. (NY 00051555!) (Zanoni & Schofield 1981).