Psilocybe pelliculosa is a species of fungus in the family Hymenogastraceae. The fruit bodies, or mushrooms, have a conical brownish cap up to in diameter atop a slender stem up to long. It has a white partial veil that does not leave a ring on the stem. American mycologist Alexander H. Smith first described the species in 1937 as a member of the genus known today as Psathyrella; it was transferred to Psilocybe by Rolf Singer in 1958. Psilocybe pelliculosa is found in the Pacific Northwest region of the United States and Canada, where it grows on the ground in groups or clusters along trails or forest roads in coniferous woods. A single collection has also been reported from Finland, and also in Norway. The mushrooms contain the psychedelic compounds psilocybin and baeocystin, although at relatively low concentrations. Several mushroom species that are similar in appearance to P. pelliculosa can be distinguished by subtle differences in the form of the fruit body, or by microscopic characteristics. Taxonomy The species was first described scientifically by Alexander H. Smith in 1937 as Psathyra pelliculosa, based on specimens he collected in Washington and Oregon. The type specimen was collected near Tahkenitch Lake, Oregon, in November 1935. In a 1941 publication, Smith revised his opinion, and considered the species to be the same as Hypholoma silvatica (later Psilocybe silvatica), as he thought that the slight differences between the two were of no taxonomic significance. After reevaluating these two species in addition to several others closely related, Rolf Singer and Smith later reestablished the taxon and transferred it to Psilocybe in 1958. Psilocybe authority Gastón Guzmán classified the species in the section Semilanceatae, a grouping of related species characterized by having roughly ellipsoid, usually thick-walled spores, and lacking pleurocystidia. The specific epithet pelliculosa is derived from the Latin pellicula, meaning "film", and refers to the gelatinous pellicle of the cap. The mushroom is commonly known as the "conifer Psilocybe" or the "striate Psilocybe". Description The cap of P. pelliculosa is initially sharply cone-shaped, and expands slightly over time to become broadly bell-shaped, but it never expands to become completely flat. The cap margin is pressed against the stem initially, and for a short time is appendiculate (has partial veil fragments hanging from the margin). The caps of mature specimens are smooth, sticky, and have translucent radial striations that reach dimensions of in diameter. The color