Closed pileus up to 8 x 5 mm, brown, yellow-brown to dark-brown at centre (Mu. 10 YR 3/3 to 6/6, K. & W. 5E7, 5D8), paler towards margin; pileus up to 10 mm in diam. when expanded. Brownish granular-flocculose veil present on pileus. Lamellae free, narrow, rather distant, white to blackish. Stipe 25-50 x 0.5-1 mm, whitish, vitreous, sparsely pubescent from setulae.
Spores [20,1,1] 12.7-16.6 x 7.2-8.5 µm, av. L= 14.7, av. B= 7.8 µm, Q= 1.70-2.10, av. Q= 1.90, ellipsoid to oblong in front view; germ pore distinctly eccentric, c. 2.3 µm wide. Basidia 14-38 x 9-11 µm, 4-spored. Pseudoparaphyses not noted. Cheilocystidia 25-55 µm in diam., vesiculose. Pleurocystidia absent. Pileocystidia 50-120 x 8-21 µm, ventricose-lageniform with narrow, tapering neck and 2.5-4 µm wide apex. Sclerocystidia absent. Velar spherocysts on pileipellis 20-35 µm in diam., often with long spine-like projections. Clamp-connections absent.
Coprinus heptemerus is recognizable by the combination of spherocysts, tapering pileocystidia, a brown pileus and a preference for dung.
The spine-like projections of the velar spherocysts are typical for C. heptemerus, which species is based on C. curtus f. macrosporus Romagn. The description of Romagnesi is, however, not very clear about the important characters of this species. M. Lange & A.H. Smith l.c. checked their material with the authentic culture of C. curtus f. macrosporus in the C.B.S. at Baarn (Netherlands) and found all details identical.