Among the bryophytes collected in northwestern Kansas by Vernon L. Wranosky of Colby, Kansas, during the summer of 1990 is a new genus and species of Pottiaceae, Ozobryum ogalalense. Subsequent collecting in the vicinity has resulted in two additional localities for this moss, one in Kansas and one in Nebraska. Ozobryum Merrill, gen. et sp. nov. TYPE: U.S.A. Kansas: Decatur County, on Ogallala Formation mortarbeds above south fork of Sappa Creek, 25 km SW of Oberlin, 39?40'N, 100?43'W, ca. 800 m, 11 Aug. 1990, Vranosky 62 (holotype, KSC; isotypes, DUKE, MICH, MO). Figures 1, 2. Planta insignis foliis obtusatis margine incrassatis quasi succulentis, cellulis utroque folii paginae grosse mamillosis, costa debili obscura utrinque cellulis mamillosis occulta bene distincta. Plants minute, growing in soft, compact cushions, to 2 cm high, dark green to yellowish green at surface of tufts, without a central strand. Leaves erect when dry, spreading at 45? or less when moist, concave, oblong-elliptic, rounded at the apex, 0.350.55 mm long, margins plane or erect. Costa ending well below the apex, thin and obscure, with 2 guide cells but no stereids, covered on both surfaces by short, bulging-mamillose cells similar to those of the lamina. Upper leaf cells bistratose (or 3-stratose) at the margins and in patches internal to the margins, rounded-hexagonal to subquadrate, ca. 7-9 Am, green and obscure, bulging on both surfaces, crowned with a broad, circular, knoblike thickening of the outer wall, centered over the lumen. Basal cells hyaline and subquadrate in a short area. Archegonial buds scattered along the stem, sometimes easily detached, with a tuft of rhizoids at the base. Perichaetial leaves smooth, ovate, acuminate, entire to unevenly serrate, the costa ending in the apex. Perigonia not seen. Paratypes. U.S.A. KANSAS: Decatur County, type locality, 30 Apr. 1991, Merrill 12888; on N-facing mortarbed cliffs, Elephant Rock, 2.5 km S of Traer, 30 Apr. 1991, Merrill 12903; Rawlins County, on mortarbeds above N fork of Sappa Creek, 22 km SE of Atwood, 11 Aug. 1990, Wranosky 69, 30 Apr. 1991, Merrill 12901. NEBRASKA: Hitchcock County, on mortarbeds exposed in arroyo, 17.6 km NW of Herndon (Kansas), 30 Apr. 1991, Merrill 12919. Voucher specimens deposited in the Reed Bryophyte Herbarium, Kans State University Herbarium (KSC). The genus name Ozobryum is derived from bryum (moss) and from the fictional Land of Oz, the creation of American author L. Frank Baum, now popularly associated with the Kansas plains. The specific epithet ogalalense refers to the Ogallala Formation, named for a locality in southwestern Nebraska. The Ogallala is the principal aquifer throughout most of the High Plains from southern South Dakota to the Texas Panhandle. The leaves of Ozobryum are highly distinctive and are characterized by their oblong-elliptic shape, the leaf cells bistratose and mamillose on both surfaces, and the reduced costa obscured on both surfaces by short mamillose cells. In its soft, dense cushions and habitat beneath ledges and in crevices on moist vertical cliff faces, Ozobryum resembles a miniature Gymnostomum. Under the hand lens the living plants have a peculiar frosted and succulent appearance due to the mamillose cells and thickened leaf margins (Fig. 2). The perichaetial leaves are strikingly different in shape from the vegetative leaves, the cells rhombic, unistratose, and smooth or only slightly roughened at the extreme apex. The female buds, which are sometimes easily detached and have a tuft of rhizoids at the base, could function as vegetative propagules, as improbable as this may seem. No brood bodies have been observed so far. At the suggestion of Richard Zander, I examined a series of 154 specimens (BUF) from Mexico and elsewhere representing his concept of Molendoa sendtneriana (B. S. G.) Limpr. (see Zander, 1977). The tropical American specimens mostly belong to the lax, glaucous-green, linear-leaved plant that corresponds to Anoectangium obtusifolium (Broth. & Par. ex Card.) Grout, illustrated by Crum & Anderson (1981). Among the Mexican specimens, however, are several that resemble Ozobryum in their small size, short blunt leaves, and thickened leaf