Look at My Mussels
Not a typo and misleading.
A glimpse at the following images might make you think they are shellfish aka bivalve molluscs.
In fact, they are tiny (ca 1mm) fungal fruiting bodies of a weird genus in the Ascomycetes. The widest FOV here is 7mm.
[i]Hysterium[/i] is represented by at least four species in the UK* and the spores would have to be examined and measured to determine which this is. I have left the material unexamined since I collected it from some rotten willow wood on 12 March.
For the specialist:
One of the characteristics of the genus is this coal-like appearance.
Olympus EM-1 (manual mode), Laowa 25mm f2.8 2.5x-5x ultra-macro at x2.5, x3 or x5, and f8or f11, twin TTL flash hand-held.