Summary:
Features in the Menser(1) description include 1) a bell-shaped, appendiculate cap that never expands to flat, the cap colored brown or dark olive gray and drying pallid buff, 2) white gills when young [that soon become mottled blackish from spores], 3) a slender, hollow, whitish to smoky gray, pruinose stem with a somewhat striate top, and 4) growth on dung. Panaeolus sphinctrinus is a member of the Panaeolus campanulatus group, considered by Gerhardt (1996), Stamets(1), and Breitenbach(4) to be conspecific under the name Panaeolus papilionaceus. Panaeolus sphinctrinus as considered by Moser(1) and Hansen, L.(2) includes Panaeolus campanulatus sensu. auct. Schalkwijk-Barendsen (who along with Courtecuisse(1) and Menser(1) does distinguish it from P. campanulatus) says it occurs throughout the Pacific Northwest but is widely scattered. 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 but has not been documented by DNA from the Pacific Northwest yet, (D. Miller, pers. comm.).

Gills:
adnate, crowded; white when young, (Menser), adnate, ascending, close; black, edge whitish, (Courtecuisse), adnate, relatively narrow; gray, then black with white edges, (Schalkwijk-Barendsen), narrow, with whitish edges, (Moser), rather narrow, ascendent, (Hansen)

Stem:
2.5-7.5cm x 0.2-0.4cm, straight and equal or base slightly widened, stem hollow, fragile; "whitish to dark smoky gray, lighter near the top, darkening from the bottom as it ages"; "smooth, polished and covered with a fine white powder", top somewhat striate, base covered with white mycelium, (Menser), up to 12cm long and 0.4cm wide; blackish brown ground color; white pruinose, (Courtecuisse), up to 10cm long and 0.3cm wide, widening slightly toward base; brown to brownish gray, (Schalkwijk-Barendsen), 6-10cm x 1-2cm, grayish or red-brownish; pruinose in upper part, (Moser), 2-10cm x 0.1-0.3cm, long, rigid; colored as cap or slightly darker; pruinose, (Hansen)

Veil:
leaves marginal remnants on cap (Menser), no ring (Schalkwijk-Barendsen)

Microscopic spores:
spores 14-18 x 8-11 microns, (Moser, who included P. campanulatus in P. sphinctrinus), 14-18 x 8-10 microns, elliptic to citriform [lemon-shaped], (Hansen who also included P. campanulatus in P. sphinctrinus), [presumably smooth, presumably with germ pore]

Spore deposit:
black (Schalkwijk-Barendsen)

Notes:
There are collections from BC at the University of British Columbia (one designated as var. minor), as well as a collection from AB. There are collections from WA, ID, and NM at the University of Washington. There is a collection from OR at Oregon State University.

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