Rhizaspis arcuatus
Rhizaspis arcuata (Penard, 1902) (= Pamphagus arcuatus)
Diagnosis: Shell ovoid with a flexible, colorless, hyaline membrane; fundus tapering into a more or less sharp point; test in cross-section flattened; aperture usually between folds and flexible; plasma fills the test completely; nucleus vesicular or ovular; filopodia usually few, long and strait.
Dimensions: 86-90 µm
Habitat: Freshwater, sediment.
Remarks: I don’t think that this is a separate species, but identical to P. scutigera.
Drawing Penard (1902
Rhizaspis scutigera, both specimens from the same sample. The left hand specimen has a pointed fundus. Maybe Penard thought this form to be a separate species.