Summary:
Features include 1) a conic or bell-shaped cap that is pale tan-brown or dark smoky, fading to whitish, often pitted or with raised ribs or wrinkles, and often appendiculate, 2) purplish gray to blackish brown, often mottled gills with white edges, 3) growth on dung or heavily manured soil, and 4) blackish spore deposit. The online Species Fungorum, accessed September 12, 2012 corrected the spelling to P. retirugus. Panaeolus retirugis was considered by Gerhardt 1996, Stamets(1), and Breitenbach(4) to be a synonym of Panaeolus papilionaceus. In Gminder(1) it is combined as Panaeolus papilionaceus var. retirugus (Fr.) Gminder. According to D. Miller, in the Pacific Northwest only one species has so far been documented by DNA sequencing and is most likely to be Panaeolus papilionaceus. Pacific Northwest collections labeled Panaeolus campanulatus and Panaeolus sphinctrinus so far have the same DNA sequencing. Panaeolus papilionaceus var. retirugis has different DNA and has been recorded from the Pacific Northwest but according to D. Miller, pers. comm. has not yet been documented by DNA.

Cap:
2-3cm across, subhemispheric [nearly hemispheric] when young, becoming broad as it ages; "pale gray, as it ages tinged pink, darker near the disc and shining when dry"; smooth or cracked, fragments from the partial veil may be attached or hanging from margin, (Menser), 2-3cm across, +/- hemispherical; whitish to grayish, ochraceous centrally; cracked when old, (Moser), 2-3cm high, bell-shaped to hemispheric; "whitish or very pale brownish"; "finally often cracking into irregular patches, margin dentate", (Hansen), whitish to dirty ivory, margin briefly fibrillose-toothed, (Courtecuisse), (1)2-5(6)cm across, obtusely conic, becoming bell-shaped when old, occasionally with obtuse umbo; not particularly hygrophanous, brownish to reddish brown, often with some grayish tones, "finally grayish cinnamon buff, while often staying more tawny at disc"; "moist to smooth when wet but soon dry", relatively smooth when young, may be finely wrinkled to horizontally cracked when very mature, exposing lighter colored flesh, margin decorated with whitish tooth-like remnants of the partial veil, (Stamets)

Flesh:
thin and brittle (Menser), thickest under disc and thinning toward cap margin; nearly colored as cap, (Stamets)

Gills:
adnate, crowded, broad; purplish gray at first then blackish brown, (Phillips), adnate or adnexed, close; pallid then darkening and mottled, edge white; edge downy, (Menser)

Stem:
9-15cm x 0.3-0.7cm, "hollow; whitish to pale gray; densely pruinose for most of its length", beaded in upper part with droplets when fresh, (Phillips) 4-6cm x 0.2-0.4cm, straight, equal or base may be slightly enlarged, stem hollow, stiff, fragile; whitish becoming purplish when old, base darker; "polished and finely powdered, no veil remnants, apex striate", (Menser)

Veil:
veil remnants may be attached or hanging from margin, (Menser)

Odor:
not distinctive, (Phillips)

Taste:
slightly foul, (Phillips)

Microscopic spores:
spores (11)12-16(18) x 8-11 microns, lemon-shaped, with apical germ pore, (Phillips)

Spore deposit:
blackish (Phillips)

Notes:
The University of British Columbia has collections from BC and Oregon State University has collections from OR and CA.

EDIBILITY

no (Phillips)

Synonyms and Alternate Names:
Panaeolus retirugis Fr..