Summary:
Features include grayish to brownish gray cap at first clothed with white to grayish hairs or fibrils of universal veil, and finally deliquescing, free pallid gills that become grayish then deliquesce, white stem that may at first be clothed with white hairs, and blackish spore deposit. Coprinopsis lagopus was in Section Lanatuli of Coprinus sensu lato. The group includes Coprinopsis cinerea (woodland habitat, spores 9-15 x 5.6-8.1 microns, or used as synonym for C. fimetarius L. per Fr.), Coprinus fimetarius (dung habitat, spores 10.0-15.6 x 6.2-9.2 microns, but may be the same species as Coprinopsis lagopus (Fr.) Fr. which grows on the ground), Coprinopsis lagopides (woodland habitat, said to frequent burn sites, spores 6.2-9.4 x 5.0-6.3 microns), Coprinopsis lagopus (habitat does not include dung in most descriptions, but may be the same species as Coprinus fimetarius that grows on dung), Coprinus macrorhizus (dung habitat, rooting stem), and Coprinopsis tectispora (thick-walled spores). C. macrorhizus may also be synonymous with C. lagopus. C. fimetarius could instead be the same species as Coprinopsis cinerea as the habitat is the main difference. The description derived from Arora(1).

Gills:
"more or less free, narrow, fairly close"; "pallid soon becoming grayish, then black and inky (but in dry weather merely withering)"

Stem:
4-15(20)cm x 0.2-0.5cm, equal or widening downward, very fragile, hollow; white, at first with minute hairs like cap, base with long, woolly, white hairs

Veil:
partial veil absent or fleeting; hairs or fibrils of universal veil on cap

Microscopic spores:
spores 10-13 x 6-7 microns, elliptic, smooth, (Arora), or including some other members of group, spores 6-13 x 5-7 microns

Spore deposit:
blackish

Notes:
Members of this group are widely distributed through the Pacific Northwest, best documented for WA and BC. They occur elsewhere in North America, and elsewhere in the world including Europe, Asia, and North Africa (Breitenbach).