Pileus 5--15 x 3--13 mm when still closed, expanded up to 25 mm in diam., first ellipsoid or (broadly) ovoid, entirely covered with sordid white to pale greyish, hairy floccose veil, then campanulate to (plano-)convex, grey-brown or greyish beige (first Mu. 10 YR 4/3, then between 6/3 and 6/4 with darker centre: 5/4; clefts pale pure grey), strongly sulcate-striate; expanding pileus near margin with copious flocks of whitish, fibrillose veil, towards centre with numerous, strikingly reflexed, squamulose scales of veil, whitish, with pale ochre tips. Lamellae, L = 24--50, l = 0--1, free, up to 4.5 mm wide, crowded, first whitish, then dark reddish brown with conspicuous white edge, finally black. Stipe up to 35 x 1.5--4 mm, usually short and solid, white, hollow, hairy floccose, slightly broadening towards not or slightly bulbous base.
  Spores [100,5,3] 8.3--12.7 x 6.2--9.3(--10.3) x 6.0--7.8 µm; Q = 1.20--1.75, av. Q = 1.30--1.55; av. L = 10--11.3, av. B = 7.2--8.1 µm, av. W = c. 7.1 µm, (broadly) ellipsoid or ovoid with rounded base and apex, dark red-brown, and central, c. 1.3 µm wide germ pore. Basidia 24--65 x 7--12 µm, 4-spored, surrounded by 3--6 pseudoparaphyses. Pleurocystidia 55--115 x 20--42 µm, oblong, ellipsoid, subglobose or (sub)cylindric. Cheilocystidia 20--100 x 15--32(--40) µm, oblong, (sub)globose, ellipsoid, ovoid, broadly subcylindric or slightly utriform. Pileipellis made up of inflated, sausage-shaped elements, 20--100 x 4--30 µm. Veil made up of long chains of inflate, cylindric, oblong to ellipsoid elements, 25--100 x 5--40 µm. Clamp-connections present.

Habitat & distribution

  In yellow dunes, subfasciculate on dead leaves of Ammophila arenaria. Very rare in the Netherlands and in France.

Remarks

  The small basidiocarps with remarkable short stipe, the rather broad spores with regard to their length and the habitat on Ammophila arenaria are characters to identify Coprinus ammophilae.
  The studied type-material was in bad condition. Cystidia could not been found in the material. The spores in collection Arnolds 6473 are somewhat broader (av. Q = 1.30--1.35) than in the type collection (av. Q = 1.35--1.40). In collection Bas 8730 the spores are oblong (Q = 1.55) in frontal view, the macroscopical characters either agree in most respects, as well as the habitat. The colours noted in the description are from this collection. Although the basidia, pleuro- and cheilocystidia are larger in coll. Bas 8730 and the spores narrower, we include this collection for this moment in the variability of Coprinus ammophilae on account of the small basidiocarps and the typical habitat on Ammophila arenaria.