The identity of Zygella S. Moore, a genus of Iridaceae of Mato Grosso, Brazil, has never been satisfactorily established. Plants described by S. M. Moore in 1895 as Zygella graminea appear to us to be conspecific with Larentia linearis (Kunth) Klatt, type species of Larentia Klatt, a plant well represented in herbaria, mostly from grasslands of Venezuela. We reduce Zygella to synonymy in Larentia, and Z. graminea becomes a synonym of L. linearis. A second species, Z. mooreana Hoehne, described in 1910 and also from Mato Grosso, is likewise conspecific with L. linearis and a lectotype is designated for that species. Cypella mexicana C. V. Morton & R. C. Foster, which shares the characters of Larentia, is transferred to the genus as L. mexicana (C. V. Morton & R. C. Foster) Goldblatt; with this addition, Larentia now includes three species.