Generic short diagnoses:
Minute, whitish, downy discomycetes on dung with characteristic multi-spored asci cracking longitudinally to a circular ring structure. Most common during winter.
Species example:
Ascozonus woolhopensis - asci apex before and after spore discarge
The picture originates from the MycoKey 2.0 DVD. Here you will also find a larger picture along with a detailed generic description, references and an interactive, synoptical key to genera.