Cap 5-14 cm tall, 2.5-4.5 cm broad, columnar, becoming bell-shaped; surface dry, white with a brown central disc, breaking up into coarse, white and brown, recurved scales; flesh thin, white, and soft; odor and taste mild.
Gills adnexed to free, crowded, white, becoming pink, then deliquescing from the margin into a black, inky liquid.
Stipe 8-20 cm long, 1-1.5 cm thick, white, smooth, hollow, equal to bulbous at base, veil white, membranous, usually sliding to the bottom of the stipe.
Spores 12-16 x 7-8 µm, smooth, elliptical with an apical pore; spore print black.
Scattered, grouped, or in dense clusters on disturbed ground or grassy areas; found frequently along roadsides, paths and in playing fields; fruiting any month of the year when moisture is available but most abundant soon after the fall rains.
Edible and choice, but must be cooked quickly before the caps turn to ink.
With its distinctive columnar, shaggy cap which dissolves into ink at maturity, Coprinus comatus is one of the easiest of all mushrooms to recognize. Coprinopsis atramentaria, another inky cap, is somewhat similar, but has a smooth to fibrillose, not scaly cap surface, and lacks the elongated cap shape of C. comatus.