Geastrum minimum

Geastrum minimum, the tiny earthstar, is an inedible species of mushroom belonging to the genus Geastrum. Although rare, it is widespread in Europe, where it occurs in a range of habitats. It is a priority species in the UK, where it has been found in the sand dunes at Holkham [National Nature Reserve].
The species was first described by Lewis [David de Schweinitz] in 1822.

Description

are initially roughly spherical before the outer peridium splits to form a star with 6–11 "rays". When opened, the diameter of the fruit body is. The inner spore sac is spherical or egg-shaped, and measures. The more-or-less round spores measure 5–5.5–4–4.5 μm and have warts on their surface.