Etym.: The name refers to the large size of the spore-sac.
Spore-sac large, up to 26 x 18 mm, easily separable from the stem. Exoperidium hyphal, forming an agglutinated layer of sand and hyphae which slowly wears off. Endoperidium almost white, smooth, tough. Mouth circular, large, up to 3 mm diam, not projecting or very slightly so. Socket conspicuous, separated from the stem, with an entire membrane which may become unevenly denticulate. Gleba cinnamon. Stem up to 90 x 8 mm, squamose (Battarraea-type), or striate-quartered, concolorous, tapering towards the base, where it exhibits a very conspicuous and large volvoid structure.
Endoperidium formed by much septate hyphae slightly enlarged at the septa, more slender than the capillitial threads, disjointable. Spores globose to elliptic, asperulate under L.M., coloured, 4.3-5.1 Âµm diam. Under SEM, the ornamentation appears formed by uneven, appressed tubercles or verrucae which vary in size, some anastomosed in cristae and with a notorious apiculus which is truncate and basally widened. Capillitium light sepia when observed under low power, more diluted with high power, branched, septate; threads very thick-walled, lumen visible in some, but solid in most, disjointable and hardly at all swollen at the scant, coloured septa; 3.3-10.1 Âµm diam.
Habitat: sandy soil in arid regions.
Distribution: North America: SW United States. South America: S Argentina.
Holotype: United States: New Mexico, White Sands Nat'l Monument, W of Administration Bldg., leg. Long, 22.IV.1942 (BPI!).