Difflugia claviformis (Penard, 1902)
Diagnosis: test pyriform, compressed, with a distinct aboral protuberance, colorless, composed of small to large pieces of quartz; pseudostome surrounded by small particles.
Dimensions: Penard (1902) 380-450 µm; my measurements: 380-434 µm.
Ecology: In sediments of ditches.
Remarks: Shells of Difflugia claviformis seem to be rare. I found this species only in the sediment of a ditch in the nature reserve Naardermeer in the Netherlands. I am not convinced that this is a separate species. I always found it together with specimens of Difflugia nodosa. Probably both species are identical. Further records are necessary.
I’m not convinced that the species below belong to D. claviformis.