On the type of Coprinus xenobius
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Original description
Coprinus xenobius P.D. Orton in Notes R. bot. Gdn Edinb. 35: 148. 1976 (Notes on British agarics VI). Isotype: Scotland: Perthshire, Camghouran, on cow dung, 11 June 1972, P.D. Orton 4504 (E).

A sociis sporis et cellulis veli interdum diverticulatis distinguitur. Pileus 2-7 x 1-4 mm, ellipsoideus vel cylindrico-ellipsoideus, dein expanso-convexus vel depressus 2-8 mm latus, interdum ad marginem radialiter fissus, ex albo albidus saepe ad discum griseo-luteolobrunneus dein grisescens, primo e velo albo piloso-tomentosus dein ± adpresse minute flocculoso-fibrillosus vel laxe elongato fibrilloso-squamulosus, senectute ± laevis et circa discum striato-sulcatus et interdum ad marginem radialiter fissus. Lamellae xa albidis griseo-luteolobrunneae dein nigrescentes. Stipes 20-40 x 0.3-2 mm, aequalis vel ad basim leviter incrasssatus, albus dein hyalinus vel griseus, primo totus albo vel albido flocculoso-fibrillosus dien glabrescens.
Odor nullus. Sporae in cumulo fusco-brunneae vel fusco-nigrae.
Sporae ellipsoideae vel cylindrico-ellipsoideae (9-)10-13.5 x (5-)5.5-6.5 µm, aliquantum crasso-tunicatae, poro germinativo medio. Basidia 4-sporigera. Cystidia aciei lamellarum sphaeropedunculata, vesiculosa vel pyriformia, 14-54 µm lata. Cystidia faciei lamellarum ± cylindrica interdum ad apicem angustiora, 58-100 x 20-30 µm, ad apicem 15-25 µm lata. Cellulae veli pilei anguste-tunicatae hyalinae cylindricae vel leviter fusiformes interdum diverticulatae, 3-12(-14) µm latae.
Perthshire: Camghouran, ad fimum vaccinum vetustum, 22 May 1972, Orton 4501 (holo. E.); Inverness-shire: Nethy Bridge, 4 July 1972, Orton 4503 (E).

English description from British Fungus Flora, Coprinaceae: part 1: Coprinus: 52. 1979. No 30.

C. xenobius P.D. Orton in Notes R. bot. Gdn, Edinb. 35: l48. 1976. Fig. 87. Icon.: none. Fig.: none.

Cap at first 2-7/l-4 mm ellipsoid or cylindric-ellipsoid, then expanded-convex to depressed, 2-8 mm broad, sometimes splitting radially at margin, at first white then whitish often clay-buff at centre, turning pale then deep grey as spores mature, but dirty whitish or pale grey-cream after spores have been shed, at first white pilosetomentose from veil, then ± adpressedly finely flocculose-fibrillose, either as fairly long loosely entwined fibrils or as scattered easily separable loosely interwoven patches, ± smooth at mature, becoming striate-sulcate from margin inwards. Gills whitish then clay-buff, soon fuscous to violaceous-black. Stem 20-40/0.3-l mm, equal or slightly swollen at base, white then hyaline or grey, entirely white or whitish flocculose-fibrillose when fresh, becoming ± smooth except at extreme base. Smell none. Sporeprint date-brown or cigar-brown to fuscous black. Spores dark red-brown, ellipsoid or cylindric-ellipsoid, (9)10-l3.5/(5-)5.5-6.5 µm rather thick-walled, germ-pore central. Basidia 4-spored. Marginal cystidia sphaeropedunculate or vesiculose to cylindric-pyriform 14-54 µm broad. Facial cystidia ± cylindric often with slightly narrower apex, 58-l00/20-30 µm, apex 15-25 µm broad. Cap cuticle of radially arranged ± cylindric cells 6-l8 µm broad. Veil on cap of branched hyphae of cylindric or slightly fusiform sometimes diverculate thin-walled hyaline cells 3-12(-14) µm broad.
Clamp-connections none seen. Genetics unknown.
Habitat on old cow dung; gregarious. So far only recorded from Perthshire and Inverness-shire in May and June. Doubtless widespread but easily overlooked since it often appears on the undersides of the old dung-masses, and may be summer fruiting.

It differs from the other very small dung-inhabiting species with filamentous cap cuticle in having the veil hyphae sometimes diverculate. C. filamentifer also differs in small spores, and C. vermiculifer in having the veil at least in part of thick-walled non-diverticulate hyphae, although the spores are of similar size.

Observations:
Spores [60,3,1] 9.6-14.7 x 5.0-8.2 µm, dark red-brown, ellipsoid or cylindric/ellipsoid; Q= 1.60-2.15, av. Q= 1.80-1.95; av. L= 10.9-13.5, av. B= 5.9-7.5 µm. Germ pore central. Basidia 18-32 x 8-10 µm, 4-spored, surrounded by (3-)4-6 paraphyses. Pleurocystidia 90-125 x 20-40 µm. Cheilocystidia 60-100 x 22-40 µm. Veil 3-10(-12) µm wide, thin-walled. Clamp-connections present.

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