The cap is ovoid expanding to a conical or bell shape with age.  It is greyish brown but covered with a whitish powdery or woolly veil.

There are similar species. C pseudonivea has a pinkish cream veil

Photograph from top down, in side view and from underneath to show gills and full length of stipe.  Note habitat and substrate.

Grows on cow and horse dung.

Summer to autumn.

Widespread and frequent (Kibby, Vol.3, 2021)

Fairly frequent in Leicestershire and Rutland.

https://www.first-nature.com/fungi/coprinopsis-nivea.php