Macroscopic feat.:

• Cap/Pileus: 1-4 cm broad. Conic-campanulate with a distinct umbo, expanding to convex to broadly convex to nearly plane with or without an acute-to-low umbo. Margin decorated with fragile whitish remnants of the partial veil. Yellowish to pale ochraceous brown toward the disc. Surface viscid when moist from a separable gelatinous pellicle. Flesh thin, pallid.
• Gills/Lamellae: Attachment adnate to subdecurrent, close, broad. Color whitish at first, then grayish, and eventually purplish brown.
• Stem/Stipe: 35-70 mm long by 2-4 mm thick. Equal and slender. Pallid to yellowish, lighter than the cap. Surface powdered above the annular region, and initially covered with fine fibrils below, but often smooth with age. Partial veil thinly membranous, floccose, leaving an obscure evanescent annular zone of fibrils, if at all.

Microscopic feat.:

• Basidio/Spores: Dark purplish brown in deposit, subellipsoid to ellipsoid, 15-19 (22) by 10-11 µm.
• Basidia: 2-spored.
• Pleurocistidia: Absent.
• Cheilocystidia: 25-45 by 3-7 µm, cylindrical to sublageniform with a flexuous, elongated apex.

Habitat: Gregarious on dung in the fall in the Pacific Northwest. Reported from Washington, Oregon, Idaho, Michigan, and New York in the summer to early fall. Also reported from Mexico, Europe, and Asia.

Comment: The habitat preference, distinctly umbonate and yellowish cap, and the white membranous partial veil all make this species easy to recognize. Additionally, the veil remnants usually adhere to the cap margin rather than the stem, especially evident when young. See also Psilocybe semiglobata and Psilocybe fimetaria.

source - Paul Stamets "Psilocybin Mushrooms of the World"

Pictures at www.mushroomobserver.org