Type:— URUGUAY. Montevideo: bañados de Carrasco, Jan 1886, Arechavaleta 253 (lectotype MVM!, 6546, designated by Moraes & Sennikov 2021: 5, isolectotypes ZT-00008162!, ZT-00008163!, ZT-00008164!, ZT-00008165!; probable isolectotypes MVM! [Arechavaleta s.n.], US02222958! [Arechavaleta s.n.]).
Homotypic synonyms: Cyperus megapotamicus var. jaeggii (Boeckeler) K ̧kenthal ex Barros (1929: 360).
Pycreus megapotamicus var. jaeggii (Boeckeler) Guaglianone (1995: 137).
Heterotypic synonyms: Cyperus mauryi Kuntze (1898: 333).
Type:— PARAGUAY. Caaguazu: dans les marais, 7 Nov 1874, Balansa 672 (lectotype P00254389!, designated by Moraes & Sennikov 2021: 5, isolectotypes G, K). Syntypes: BRAZIL. Minas Gerais: Conceiç „o do Rio Verde, Contendas, Dec 1892, Kuntze 18 (NY00919225!); idem, Contendas, Dec 1892, Kuntze 18bis (K001174594!).
Pycreus nematodes Schrader ex Clarke (1902: 5) ≡ Cyperus megapotamicus var. nematodes (Schrad. ex C.B.Clarke) Ķkenthal ex Osten (1931: 131).
Type:— BRAZIL. In insula S. Catharinae, Chamisso s.n. [35] (lectotype LE!, designated by Moraes & Sennikov 2021: 6; isolectotype B †, Chamisso s.n. (206)). Syntype: CHILE. Prov. Ñuble, Río Diguillín, May 1878, Puga s.n. (SGO000010408!).
Cyperus jaeggii Boeckeler is accepted here as the correct name for Cyperus megapotamicus sensu Kunth ≡ Pycreus megapotamicus sensu Nees, circumscribed in a broad sense, i.e. including Cyperus mauryi and P. nematodes. Figure 42 shows Sellow’s specimens that have been taken as type of Cyperus megapotamicus sensu Kunth.
The list of forgotten names that have nomenclatural priority has not been duly finalised. Chrysocoma megapotamica Sprengel (1826: 424) is also mentioned, which has priority over Eupatorium ericoides Candolle (1836: 150) ≡ Disynaphia ericoides (DC.) King & Robinson (1971b: 124). A new combination in Disynaphia is provided: