Summary: Features include small size, an ochraceous brownish cap that becomes gray, deliquescing gills, downy white stem, growth in clumps, and (microscopically) pleurocystidia and pileocystidia. Coprinellus congregatus was in Section Setulosi of Coprinus sensu lato along with Coprinellus disseminatus, Coprinellus ephemerus, Coprinellus hiascens, and Coprinellus impatiens according to Moser. There are probably others in this section which has not been fully studied in the Pacific Northwest. The description here is derived from Moser(1).
Cap: 0.2-3cm high, fairly thin, then conic - bell-shaped; clay-colored, ochraceous-brownish, then gray, cap center leather pallid; at first lightly downy