I found this specimen in a sample from the Oppad, near Hilversum, 2020. It is similar to Psammonobiotus linearis, but lacks a clear spine at the fundus.
Actinosphaeridium spec.
Actinosphaeridium spec. Diagnosis: Cell surrounded by a membranous shell, with an outer mucous layer. Filopodia with granules, sometimes branching. Cell stalked. Ecology: I found this