Collared Earthstar - Geastrum triplex

A very large earthstar with a thick, fleshy outer part or peridium that typically splits across the rays as they open and bend downwards, often creating an inner saucer-like structure or collar under the spore-sac. The spore-ball itself does not have a collar and is not stalked.  The pore opening is fringed and is within a faintly delimited zone. 

Other Geastrum species are smaller, and do not have a collar formed by the rays breaking as they open (although some species have a collar that is part of the spore-ball).  

Photograph in habitat, from top diwn and in side view; photograph detail of pore opening; note size, habitat, substrate, and associated tree species.

Rich soil in parks, gardens, woodlands, under conifers and deciduous species.

autumn

Fairly common in Leicestershire and Rutland.

https://www.first-nature.com/fungi/geastrum-triplex.php

[Note: In some sources this species is called Geastrum michelianum; this is probably a more correct name, but it is still called G triplex on the NBN.]