Gigaspora erythropa, a newly described species, occurs commonly in sand dunes of the Atlantic coast to the USA and the Bahamas and also in a silt-loam apple orchard in New York [.+-.SA]. The species is characterized by its dark orange- to red-brown, smooth-walled spores which possess a brittle outer wall group consisting of a thick, colored exterior wall and 1 or 2 thin, hyaline walls, and a flexible inner wall group composed of a thick, pale yellow laminated wall and a thin membranous innermost wall. G. erythropa formed mycorrhizae with arbuscules but not with vesicles in pot cultures with apple, onion, sorghum and ryegrass [Pyrus malus, Allium cepa, Sorghum vulgare, Poa pratensis, respectively]. The species was also associated, but not proven mycorrhizal, with Ammophila breviligulata, Solidago sempervirens and Lathyrus japonicus var. glaber.