Notohymena pampasica n. sp. was isolated from terrestrial samples obtained from a temporary pond during its dry phase in Buenos Aires province, Argentina. The ciliates were grown in resuspended soil material and were studied in vivo and after impregnation with protargol. The species measures 84-112 × 35-42 µm. The organism cytoplasm is transparent, with many refractive cytoplasmic globules, which appear dark brown at low magnification, and are located mainly at the posterior end and the margins of the body. There are colorless refractive cortical granules in longitudinal rows at the bases of dorsal dikinetids and around ventral cirri. The contractile vacuole presents two inconspicuous collecting canals. The nuclear apparatus is composed of 2 macronuclear nodules and 2 (rarely 3) micronuclei. There are 22-29 oral polykinetids and paroral and endoral membranes arranged in a pattern typical of Notohymena. The somatic ciliature is arranged in 3 frontal, 1 buccal, 4 fronto-ventral, 3 (rarely 4) postoral, 2 pre-transverse, 5 transverse, and 2 marginal rows of cirri. Dorsally there are 6 rows of dikinetids and 3 caudal cirri. This new species primarily differs from congeners in the color and pattern of disposition of the cortical granules.Fil: Kuppers, Gabriela Cristina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División de Zoología Invertebrados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Claps, Maria Cristina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Limnología ; ArgentinaFil: Lopretto, Estela Celia. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División de Zoología Invertebrados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin
