Difflugia claviformis (Penard, 1899)
Basionym: Difflugia pyriformis var. claviformis Penard, 1899
Diagnosis: Shell subpyriform, not compressed; straight or a little curved; fundus with an aboral protuberance or shaped like a gothic arch. Composed of large, flat pieces of quartz, but pseudostome surrounded by much smaller particles. Nucleus large, with numerous small nucleoli. Zoochlorellae never present.
Dimensions: Penard (1902): length 380-450 µm; nucleus 50 µm.
Ecology: In freshwater sediment.
Remarks: Shells of Difflugia claviformis seem to be rare. Penard found his specimens only in Lake Geneva, at a depth of 20-30 m. He described his form as non compressed and without zoochlorellae.